WELLS'S 
PRINCIPLES AND APPLICATIONS 



OF 



CHEMISTRY; 



USE OF ACADEMIES, HIGH-SCHOOLS, AND COLLEGES: 

INTRODUCING 

THE LATEST RESULTS OF SCIENTIFIC DISCOVERY AND RESEARCH, AND 

ARRANGED WITH SPECIAL REFERENCE TO THE PRACTICAL 

APPLICATION OF CHEMISTRY TO THE ARTS AND 

EMPLOYMENTS OF COMMON LIFE. 



WITH TWO HUNDRED AND FORTY ILLUSTRATIONS. 



BY 

DAVID iE!%ELLS, A.M., 

AUTHOR OF "WELL6B NATURAL PHILOSOPHY," "SCIENCE OF COMMON THINGS, 
EDITOR OF THE "ANNUAL OF SCIENTIFIC DISCOVERY," ETC. 



NEW YORK: 
IVISON, PHINNEY, BLAKEMAN k CO., 

CHICAGO : S. C. GRIGGS & CO. 

1 867. 



K 



\is( A~ 



Entered, according to Act of Congress, in the year 1858, by 

IYISON & PIIINNEY, 

In the Clerk's Office of the District Court for the Southern District of New York. 



48 65 55 

JUL 16 1942 



ELECTROTYPE!) BT 

T. B SMITH & SON, 
82 & 84 Beekman-street, N. Y. 






(J/a^i^ &<&** 









fly, 



*>• 



I 



P R 




p This work has been prepared with special reference to 
the wants of students in Academies, Seminaries, and Col- 
leges, aiming to furnish just that information which will 
prove most useful and practical in their future employ- 
ments and relations of life. 

The great general principles of Chemistry, and the 
more important of the elements and their compounds, have 
been accordingly very fully discussed ; while, on the other 
hand, the custom adopted in many text-books of enumer- 
ating and describing compounds which have no practical 
value and little scientific interest, has been disregarded. 

To enable the student to understand more clearly the 
relations which Chemistry sustains to the industrial ope- 
rations of the age, and to the past and present progress 
of civilization, greater attention has been given to the his- 
tory of the science than has heretofore been customary in 
elementary text-books. 

Special care has also been taken to present the very latest 
results of scientific discovery and research, in this country 
and Europe, and to take advantage of the most approved 
methods of experimentation and instruction. 

An unusually large number of illustrations has been 

introduced, with the double purpose of rendering the 

study of the science more intelligible and attractive to 

- the pupil, and of facilitating the instructions of teachers, 



IV PKEFACE. 

especially of those not enjoying the advantage of large ap- 
paratus. 

In respect to originality the author makes little pre- 
tension beyond the arrangement and classification of sub- 
jects, and the selection of illustrations. Among the 
authorities to which he is especially indebted he would 
mention Faraday, Prof. Miller, of King's College, Lon- 
don, Graham, Kegnault, and Hayes. 



New York, May, 1858. 






CONTENTS 



PAGE 

Introduction. . 9 



CHAPTER, I. 

On the Connection of Gravity, Cohesion, Adhesion, and Capillary 

Attraction with Chemical Action 22 

Section I. — Gravity 22 

" IL— Cohesion 29 

" III. — Adhesion and Capillary Attraction 32 

" IV. — Crystallization 44 



CHAPTER II. 

Heat 56 

Section I. — Sources of Heat 60 

" II. — Communication of Heat. 63 

" III. — Effects of Heat T5 



CHAPTER III. 

Light 112 

Section I. — Nature and Sources of Light 112 ' 

" II. — Properties of Light 115 



CHAPTER IV. 
Electricity 130 



VI CONTENTS. 

INORGANIC CHEMISTRY. 

CHAPTER V. 

PACsB 

General Principles of Chemical Philosophy. 156 

CHAPTER VI. 

The Non-Metallic Elements 18-4 

Section I. — Oxygen 184 

" II. — Management of G-ases 196 

" III. — Hydrogen 199 

" IY. — Nitrogen, or Azote 219 

" V.— Chlorine 235 

" VL— Iodine 253 

" VII— Bromine 255 

" VIII.— Fluorine 256 

" IX.— Sulphur 258 

" X. — Selenium and Tellurium 268 

" XL— Phosphorus 269 

" XII.— Boron 276 

" XIII.— Silicon, or Silicium 279 

" XIV.— Carbon .282 

CHAPTER VII. 
Combustion 301 

CHAPTER VIII. 
The Metallic Elements 324 

CHAPTER IX. 

The Metals of the Alkalies 327 

Section I. — Potassium 327 

" II.— Sodium 333 

" III. — Lithium 339 

" IV.— Ammonium 339 

CHAPTER X. 

Metals of the Alkaline Earths 343 

Section I. — Barium and Strontium 343 



CONTENTS. Vll 

PAGK 

Section II. — Calcium 344 

" III. — Magnesium 349 



CHAPTER XI. 

Metals of the Earths 350 

Section I. — Aluminum . 351 



CHAPTER XII. 
Glass and Pottery 355 



CHAPTER XIII. 

The Common, or Heavy Metals 360 

Section I.— Iron 360 

" II. — Manganese and Chromium 367 

" III. — Cobalt and Nickel 370 

" IV. — Zinc and Cadmium 371 

" V.— Lead and Tin 372 

" YI. — Copper and Bismuth 377 

" VII. — Uranium, Vanadium, Tungsten, Columbium, Tita- 
nium, Molybdenum, Niobium, Pelopium, Ilmenium, 

etc 380 

" VIII. — Antimony and Arsenic 380 



CHAPTER XIV. 

The Noble Metals 385 

Section I.— Mercury 385 

" II.— Silver 388 

" HI.— Gold 392 

" IV. — Platinum, Palladium, Ehodium, Ruthenium, Os- 
mium, Iridium 395 



CHAPTER XV. 
Photography 397 



YU1 CONTENTS. 

ORGANIC CHEMISTRY. 
CHAPTER XVI. 

PAGH 

Nature of Organic Bodies 401 

CHAPTER XVII. 

Essential Immediate Principles of Plants 405 

Section I. — Vegetable Tissue, Starch, Gum, Sugar 405 

" II. — Albumen, Caseine, Gluten 421 

CHAPTER XVIII. 

Natural Decomposition of Organic Compounds 424 

CHAPTER XIX. 
Alcohol and its Derivatives 433 

CHAPTER XX. 
Vegetable Acids 450 

CHAPTER XXI. 
Organic Alkalies 455 

CHAPTER XXII. 
Organic Coloring Principles 451 

CHAPTER XXIII. 
Oils, Pats, and Resins 461 

CHAPTER XXIV. 

The Nutrition and Growth of Plants 475 

CHAPTER XXV. 

Animal Organization and Products 482 

Appendix 502 



PRINCIPLES OF CHEMISTRY, 



INTRODUCTION. 



1. Matter is the general name which has been given 
to that substance which, under an infinite variety of 
forms, affects our senses. We apply the term matter to 
every thing that occupies space, or that has length, 
breadth, and thickness. 

The forms and combinations of matter seen in the animal, vegetable, and 
mineral kingdoms of nature, are numberless, yet they are all composed of a 
very few simple substances or elements. 

2. Simple Substances. — By a simple substance, or ele- 
ment, we mean one which has never been derived from, 
or separated into, any other kind of matter. 

Sulphur, gold, silver, iron, oxygen, and hydrogen, are 
examples of simple substances or elements ; and are so 
considered because we are unable to decompose them, 
convert them into, or create them from, other bodies. 

No known force has yet extracted any thing from sulphur but sulphur, or 
from gold but gold ; but if by any method these substances could be broken 
up into two or more factors, or component parts, they would cease to be re- 
garded as elementary. 

The number of the elements, or simple substances, with 
which we are at present acquainted, is sixty-two. 

These substances are not all equally distributed over 
the surface of the earth : many of them are exceedingly 
rare, and known only to chemists. Of the whole number, 
from ten to fifteen only are concerned in the formation of 

Questions. — What is matter ? What is a simple substance, or element ? What is the 
number of the elements? How are the elements distributed? 

1* 



10 PRINCIPLES OF CHEMISTRY. 

the great "bulk of all the familiar objects Ave see around 
ns. 

The atmosphere is made up of two-— oxygen and nitrogen — with, compar- 
atively speaking, mere traces of carbon and hydrogen : two of these, again — 
oxygen and hydrogen — give rise to water, a substance covering three fourths 
of the surface of our planet ; while the great rock masses of the earth, are 
mainly compounds of eight simple substances, viz., oxygen, silicon, alumin- 
ium, calcium, potassium, sodium, chlorine, and iron. In the composition 
also of animal or vegetable structures, the same, or a still greater simplicity 
is observed. 

3. Compound Bodies. — A Compound Body is one that 
can be separated into two or more elements, or simple 
substances. 

4. Atoms. — All matter is supposed to be composed of 
exceedingly minute particles, which can not be subdi- 
vided, or separated into parts. Such ultimate particles 
are termed Atoms. 

No one has ever seen an atom ; no one has ever been able to recognize 
through the agency of the senses a portion of matter so small that it could 
not in some way be made smaller ; yet the evidence on this subject, derived 
mainly from modern investigations in chemistry, is of such a character that 
there can be no reasonable doubt that all matter is ultimately composed of 
indivisible parts, or atoms. The nature of this evidence will be mentioned 
hereafter. 

Simple, or' elementary bodies, have simple atoms, and 
compoand bodies compound atoms. The atoms of each 
substance undoubtedly differ in weight, and may possibly 
differ in size and form. 

Mol'e-cules. — We use the term Molecule, or Particle 
of matter, to designate very small quantities of a substance, 
not meaning, however, the ultimate atoms. A molecule, 
or particle of matter, may be supposed to be formed of 
several atoms united together. 

The extent to which matter can be divided, and perceived by the senses, is 
most wonderful. A grain of musk will fill the air of a room for years with 
fragrant particles, without suffering any considerable loss of- weight. In the 
manufacture of gilt wire, used for embroidery, the amount of gold employed 
to cover a foot of wire does not exceed the 720,000th part of an ounce. 

Questions:— What is a Compound Body? What is supposed to be the ultimate con- 
stitution of matter ? What are atoms ? What is a molecule ? Illustrate the divisibility 
of matter. 



INTRODUCTION. 11 

The manufacturers know this to bo a fact, and regulate the price of their wiro 
accordingly. But if the gold which covers one foot is the 720,000th part of 
an ouuce, the gold on an inch of the same wire will be only the 8,640,000th 
part of an ounce. We may divide this inch into one hundred pieces, and yet see 
each piece distinctly without the aid of a microscope : in other words, we seo 
the 864,000,000th part of an ounce. If we now use a microscope, magnifying 
five hundred times, we may clearly distinguish the 432,000,000.000th part of 
an ounce of gold, each of which parts will be found to have all the characters 
and qualities which are found in the largest masses of gold. 

Some years since, a distinguished English chemist made a scries of experi- 
ments to determine how small a quantity of matter could be rendered vis- 
ible to the eye, and by selecting a peculiar chemical compound, small portions 
of which were easily discernible, he came to the conclusion that he could dis- 
tinctly see the billionth part of a grain. This quantity may be represented in 
figures thus, 1,000,000,000,000, but the mind can form no rational conception 
of it. 

5. Porosity. — No two atoms of matter are supposed to 
touch, or be in actual contact with each other, and the 
openings or spaces which exist between them are called 
Pores. This property of bodies, according to which their 
atoms are thus separated by vacant places, is called Po- 
rosity. 

The reasons for believing that the atoms or particles of 
matter do not actually touch each other, are, that every 
form of matter, so far as we are acquainted with it, can, by 
pressure, be made to occupy a smaller space than it origin- 
ally filled. Therefore, as no two particles of matter can 
occupy the same space at the same time, the space, by 
which the size or volume of a body may bo diminished by 
pressure, must, before such diminution took place, have 
been filled with openings, or pores. Again, all bodies ex- 
pand or contract under the influence of heat and cold. 
Now, if the atoms were in absolute contact with each 
other, no such movements could take place. 

The porosity of liquids may be proved by mixing together equal measures 
of strong alcohol and water ; when the resulting compound will be found to oc- 
cupy considerably less space than its two constituents did separately : — in other 
words, a gallon of each liquid mixed will not form two gallons of compound. 

6. Inertia.— Matter of iijelf has no power to change its 

Questions. — What are pores ? Are the particles of matter in absolute contact ? How 
may the porosity of liquids be shown ? Has matter any power in itself to change its con- 
dition ? 



12 PRINCIPLES OF CHEMISTRY. 

state, or form. If a body is at rest, it can not of itself 
commence moving ; and if a body be in motion, it can 
not of itself stop, or come to rest. Motion, or cessation 
of motion in a body, or any other change of its condition, 
requires a power to exist independent of itself. 

As the cause of all the changes observed to take place 
in the material world, we admit the existence of certain 
forces, or agents, whicli govern and control all matter. 

7. Force is whatever produces or opposes motion or 
change in matter. 

Causes of Change. — AH the changes which we observe to 
take place in matter maybe referred to the following causes, 
or forces :-- The Attraction of Gravitation, Molecu- 
lar Forces — or forces acting only between molecules, or 
particles of matter at insensible distances — Forces devel- 
oped through the agencies of Light and Heat, the At- 
tractive and Repulsive Forces of Electricity and 
Magnetism — and finally, a force or power which exists only 
in living animals and plants, which is called Vital Force. 

Concerning the real nature of these forces, we are entirely ignorant. "We 
suppose, or say, they exist, because we see their effects upon matter. In the 
present state of science, it is impossible to know whether they are merely 
properties of matter, or whether they are forms of matter itself, existing in 
an exceedingly minute, subtile condition, without weight, and diffused 
throughout the whole universe. The general opinion, however, among scien- 
tific men, at the present day, is, that these forces, or agents, are not matter, 
but properties, or qualities, of matter. 

8. Gravitation.— The Force of Gravitation, or the At- 
traction of Gravitation, is the name applied to that force by 
which all the bodies in the universe at sensible distances 
attract and tend to approach each other. Gravitation dif- 
fers from all other forces in the fact that its influence is 
universal ; that it acts at all times, upon all matter, and 
at all distances. 

The force of gravitation belongs equally to the smallest atom and to the 
largest world, producing those attractions which bind masses of matter to- 

Questions.— What- occasions change in matter ? What is force ? Enumerate the great 
forces of nature. What do we know concerning these forces ? What is gravitation ? Is 
the force of gravitation universal ? 



INTRODUCTION. 13 

gethcr, and restrict the motions of the planets to regular orbits. It is the 
force which draws a small body, free to move, toward a larger. 

Terrestrial Gravitation is that force by which all bodies 
upon the earth are attracted toward its center. s 

The measure of this force, or the strength with which} 
a body upon the earth is attracted toward its center, is/ 
called Weight. 

The attractive force which the earth exerts upon a bod}- is proportioned to 
its mass, or to the quantity of matter contained in it, and as weight is merely 
the measure of such attraction, it follows that a body of a large mass will be 
attracted strongly, and possess great weight, while, on Uio concrary, a body 
made up of a small quantity of matter, will be attracted in a less degree, and 
possess less weight. We recognize this difference of attraction by calling 
the one body heavy and the other light. 

9. Varieties of Force. — Mo-lee'ular, or, as they are 
sometimes called, Internal Forces, are distinguished from 
all the other Forces which act upon matter, in this respect 
— that they act upon particles or molecules of matter at 
immeasurably small distances only. 

The forces developed through the agencies of heat, 
light, electricity, and magnetism, are diverse in their na- 
ture, and affect different forms of matter differently. They 
differ from the force of gravitation inasmuch as their in- 
fluence does not appear to be universal or constant, and 
is apparently limited by distance. They differ, especially, 
from molecular forces, inasmuch as their influence upon 
matter is exerted at sensible distances. 

It is not at all certain that the forces which act upon matter, as above enu- 
merated, are all separate and independent. Their connection with each other 
is most intimate, and there is reason for believing that some of them are only 
different manifestations of the same agent, or principle. 

10.. Molecular Forces,— Under the designation of molec- 
ular forces are especially included four different manifes- 
tations of force, or, as they are usually called, varieties of 



Qttkstions. — What is Terrestrial Gravitation ? What is Weight ? What are the pecu- 
liarities of molecular forces? What are the peculiarities of the forces developer! hy the 
agencies of light, heat, electricity, and magnetism? Is it certain that the forces enu- 
merated are all independent principles ? What are included under the head of mole- 
cular forces ? 



14 PRINCIPLES OF CHEMISTRY. 

attraction. These are Cohesion, Adhesion, Cap'illary 
Attraction, and Affinity. 

Although essentially differing from each other, these forces all agree in one 
remarkable particular — and that is, their influence upon matter is exerted 
only at distances which are immeasurable, or insensible. If the particles of 
a body are separated from each other to the slightest appreciable degree, the 
influence of these attractive forces is instantly neutralized or destroyed. 

11. Cohesion, or Cohesive Attraction, is that force 
which binds together atoms of the same kind of matter 
to form one uniform mass. 

The force which holds together the atoms of a mass of iron, wood, or stone, 
is cohesion, and the atoms are said to cohere to each other. 

The effort required to break a substance is a measure 
of the intensity or strength of the cohesive force exerted 
by its particles. 

When the Attraction of Cohesion batwecn the particles 
of a substance is once destroyed, it is generally impossible 
to restore it. Having once reduced a mass of wood or stone 
to powder, we can nor make the minute particles cohere 
again by inertly pushing them into their former position. 

In some instances, however, this may be accomplished by resorting to va- 
rious expedients. Iron may be made to cohere to iron by heating the metal 
to a high degree, and hammering the two pieces together. The particles 
are thus driven into such intimate contact, that they cohere and form one 
uniform mass. This property is called Weldixg. and belongs only to two 
metals, iron and platinum. 

12. Adhesion, or Adhesive Attraction, is that force 
which causes unlike particles of matter to adhere, or re- 
main attached to each other when united. 

Dust floating in the air sticks to the wall or ceiling, through the force of 
adhesion. When we write on a wall with a piece of chalk, or charcoal, the 
particles, worn off from the material, stick to the wall and leave a mark, 
through the force of adhesion. Two pieces of wood may. be fastened to- 
gether by means of glue, in consequence of the adhesive attraction between 
the particles of the wood and the particles of glue. 

13. Cap 'ill 'dry At traction is that variety of molecular 
force which manifests itself between the surfaces of solids 
and liquids. 



Qr-OTioxs.— What is cohesion? What is a measure of the force of cohesion ? What 
iswelding? What is adhesion? Give examples of adhesion. What is capillary attraction? 



INTRODUCTION, 



15 



Fig. 1. 




Fig. 2. 



The ordinary definition of Cap'illary Attraction is, that form of attraction 
which causes liquids to ascendabove theirlevel in capillary tubes. This, how- 
ever, is not strictly correct, as this force not only causes an elevation, but also 
a depression of liquids in tubes, and is at work wherever fluids are in contact 
with solid bodies. 

The name " Capillary Attraction" originated from the cir- 
cumstance that this class of phenomena was first observed in 
small glass tubes, the bore of which was not thicker than a 
hair, and which were hence called Capillary Tubes, from the 
Latin word capillvs, which signifies a hair. 

The simplest method of exhibiting capillary attraction is to 
immerse the end of a piece of thermometer tube in water (see 
Fig. 1) which has been tinted with ink. The liquid will be 
seen to ascend, and will remain elevated in the tube at a con- 
siderable height above the surface of the liquid in the vessel. 

The height to which water will rise in ca- 
piliary tubes is in proportion to the smallness jj^ 
of their diameters. 

This is clearly shown by the 
following simple experiment. If 
two plates of glass, A and B, 
Fig. 2, bo plunged into water 
at their lower extremities, with 
their faces vertical and parallel, 
and at a certain distance asun- 
der, the water will rise at the 
i points m and n, where it is in 
contact with the glass ; but at 
all intermediate points, beyond a small distance from the plates, the general 
level of the surfaces E, C, and D, will corre- 
spond. 

If the two plates, A and B, are brought near 
to each other, as in Fig. 3, the two curves, m 
and n, will unite, so as to form a concave sur- 
face, and the water at the same time between 
them will be raised above the general level, E 
and D, of the water in the vessel. If the 
plates be brought still nearer together, as in 
Fig. 4, the water between them will rise still higher, the force which sustains 
the column being increased as the distance between the plates is diminished. 
Illustrations of capillary attraction are most familiar in the experience of 
every-day life. The wick of a lamp, or candle, lifts the oil, or melted grease 





Qutstioxs. — How may the phenomena of cap'illary attraction he illustrated ? To what 
height will water rise in capillary tuhes ? What are familiar examples of capillary at- 
traction ? 




16 PRINCIPLES OF CHEMISTRY. 

which supplies tho flame from a surface 
often two or three inches below the point 
of combustion. 

Yv'hen one end of a sponge, or a lump of 
sugar is brought into contact with water, 
the liquid, by capillary attraction, will rise, 
or soak up above its level, into the interior 
of the sponge, or sugar, until all its pores 
are filled. 

14. Affinity is that variety of molec'ular force or attrac- 
tion which unites atoms of unlike substances into com- 
pounds possessing new and distinct properties. 

Oxygen, for example, unites with iron, and forms oxyd of iron, or iron- 
rust, a substance possessing different and distinct properties from either iron 
or oxgyen. In like manner, oxygen and Irydrogen, two gases not to be dis- 
tinguished in appearance from common air, unite to form water, a liquid. 

"When the particles of different substances are united together by the force 
of affinity, the compound formed possesses properties entirely different from 
that of its constituents, and in no respect resembles a mixture, which is 
merely a mechanical union of bodies — as when salt is mixed with sand. The 
forces of adhesion or capillary attraction may closely unite unlike particles of 
matter together, but they do not effect any change in the nature or properties 
of the particles acted upon. Affinity, on the contrary, entirely changes the 
properties of the unlike particles which it unites, and by so doing produces 
combinations which possess entirely different qualities. 

Tiie action of gravity and of the several molecular forces may be illustrated 
by referring to a particular form of matter, as, for example, water. The force 
of affinity binds together the atoms of the elements, oxygen and hydrogen, to 
constitute an atom, or molecule of water ; cohesion unites the particles of 
water thus formed into drops, or larger masses ; adhesion causes the union of 
water with the surfaces of different substances, thereby producing the pheno- 
menon which we call ; ' wetting;" capillary attraction causes water to rise 
above its level, or " soak up" as it is termed, in a sponge, or other porous 
substance ; while the force of gravity causes coherent quantities of water to 
fall as rain, or to move down inclined surfaces in the form of rivers, brooks, etc. 

15. Repulsion. — In opposition to the several attractive 
forces which act upon matter, a repulsive force also ex- 
ists, the tendency of which is to separate the particles of 
matter from one another. 



Questions — What is affinity ? What are illustrations of affinity ? How do the com- 
pounds of matter formed through the force of affinity differ from a mixture ? How do 
the forces of adhesion and capillary attraction differ from affinity ? How may the ac- 
tion of gravity and the molecular forces be illustrated ? What force acts in opposition to 
the attractive forces ? 



INTRODUCTION. 17 

The resistance experienced in attempting to compress a substance is the 
result of the opposition of the repulsive force which pervades its particles 
and the effort required to effect a compression is a measure of the intensity 
of the repulsive force. 

A dew-drop resting upon a leaf is not in actual contact with its surface, 
but is sustained at a little distance above it by the force of repulsion. In- 
genious experimentation has proved that when two glasses, one slightly con- 
vex and the other flat, are placed upon each other, and pressed together with 
a force of 1,000 pounds to the square inch, they still remain at a distance 
from each other of the thickness of the top of a soap-bubble before it bursts, 
or at least 1-445 0th of an inch. If we compress a certain quantity of gas, as 
common air, and then allow it to dilate, by removing all restraint, it will ex- 
pand without limit, and fill every really empty space which is open to it. 
This takes place through the agency of an internal repulsive force, which 
tends to drive the particles from one another. 

It is not definitely known whether the repulsive force, which appears to 
influence, under certain circumstances, the particles of all matter, is a separate 
and independent principle, or whether it is the result of the action of heat or 
of electricity, or of both these forces combined. Heat, in its influence upon 
matter, always acts as a repulsive force, and is always opposed to the influ- 
ence of cohesion. 

16. Elasticity. — That property of bodies known as Elas- 
ticity is the result of the joint action of the repulsive and 
attractive forces ; and substances are said to be more or 
less elastic, according to the facility with which they re- 
gain their original form and dimension after the force 
which has compressed or extended them is removed. 

17. Three Forms of Matter.— According as the attractive 
or repulsive forces prevail, all bodies will assume one of 
three forms or conditions — the solid, the liquid, or the 
a'er-i-form,* or gaseous condition. 

18. Solids. — A solid body is one in which the particles 
are so strongly held together by the attractive force of 
cohesion, that the body maintains its form or figure under 
all ordinary circumstances. 

If the force of cohesion acted exclusively upon matter, every substance 
would possess insuperable solidity, hardness, and tenacity. 



A'er-i-form, having the form, or resemblance, of air. 



Questions. — What evidence is there of the existence of a repulsive force? What is 
elasticity? What are illustrations of the influence of a repulsive force? Under -what 
three forms or conditions does matter exist ? What is a solid body ? 



18 



PRINCIPLES OF CHEMISTRY, 



19. Liquids . — A liquid body is one in which the particles 
of matter are held together so slightly, by the force of co- 
hesion that; they move upon each other with the greatest 
facility. 

Ilonco a liquid can never be made to assume any particular form except 
that of the vessel in which it is inclosed. 

20. Gaseous Bodies, — An a'er-i-forrn or gaseous body is 
one in which the particles of matter are not held together by 
any force of cohesive attraction, and but for the restrain- 
ing influence of the force of gravity would entirely sepa- 
rate and move on from one another. 

A. gaseous body is generally invisible, and, like the air surrounding us, 
affords to the sense of touch no evidence cf its existence when in a state of 
complete repose. Gaseous bodies may be confined in vessels, whence they 
exclude liquids, or other bodies, thus demonstrating their existence, thou.h 
invisible, and also their impenetrability. 

21. C li a n g e of Condition . — Most substances can be made to assume 
successively the form of a solid, a liquid, or a gas. In solids, the attractive 
force is the strongest ; the particles keep their places, and the solid retains its 
form. J3u' if we heat a solid body, as for example a piece of ice, or sulphur, we 
weaken the force of cohesion which binds the particles together, and allow 
the repulsive force to prevail; the particles of the soli 1 thereby become mov- 
able upon themselves, and we say the body melts, or becomes liquid. In 
liquids the attractive and repulsive forces are nearly balanced, but if we sup- 

F IG- 5 < ply an additional quantity of heat, we de- 

stroy the attractive force altogether, and 
increase the repulsive force to such an ex- 
tent that the liquid assumes the form of a 
gas, or vapor, in which the separate par- 
ticles tend to fly off from each other. By 
reversing the process, or, in other words, 
by withdrawing the heat, we can diminish 
or destroy the repulsive force, and cause 
the attractive force again to predominate — 
the body returning to its former conditions, 
first of a liquid, then of a solid. 

The power of the repulsive force gen- 
erated by heat is strikingly illustrated in 
the conversion of water into steam. In a cubie inch of water converted into 
steam, the particles will repel each other to such an extent, that the space 




Questions — What is a liquid ? What is an a'or-i-form, or gaseous body ? Under what 
circumstances will a body assume the form of a solid, a liquid, or a gas? What experi- 
ment illustrates the repulsive power of heat. 



INTRODUCTION. 19 

occupied by the steam will be 1700 times greater tban that occupied bj the 
water. Fig. 5 illustrates the comparative difference between the bulk of steam 
and the bulk of water. 

22. Ethereal Condition . — Eecent investigations in science have ren- 
dered it probable, that matter, in addition to the throe separate states or con- 
sistencies in which it is ordinarily presented to us — solid, liquid, and gaseous — 
exists also in a fourth state, which is called the ethereal. It is supposed that 
all space — that existing between the planets and other heavenly bodies, 
equally with that existing between the atoms, or molecules of every sub- 
stance, even the most dense — is pervaded by an extremely rare, imponder- 
able, and highly elastic medium, or fluid form of matter, termed Ether. 
This substance, like air, is believed to be capable of motion, and of receiving 
and transmitting vibrations, which vibrations by their action on the ordinary 
forms of matter, are supposed to produce the phenomena of heat, light, elec- 
tricity, etc., in the same manner as the vibrations of air occasioned by a 
sounding body produce the phenomena of sound. 

23. Matter Indestructible. — All the researches and in- 
vestigations of science teach us that it is impossible by nat- 
ural operations, to either create or destroy a single particle 
of matter. The power to create and destroy matter belongs 
to the Deity alone. The quantity of matter which exists, 
in and upon the earth has never been diminished by the 
annihilation of a single atom. 

When a body is consumed by fire, there is no destruction of matter : it has 
only changed its form and position. When an animal or vegetable dies and 
decaj'S, the original form vanishes, but the particles of matter, of which it was 
once composed, have merely passed off to form new bodies and enter into new 
combinations. 

24. Force Indestructible. — Kecent investigations in 
science seem to prove that force is equally as indestructible 
as matter ; or, in other words, that there is no such thing 
as a destruction of force ; consequently the amount of force 
in operation in the earth, and possibly throughout the 
universe, never varies in quantity, but remains always the 
same. 

Some of the reasons which have led to a belief in the indestructibility of 
force may be stated as follows : — 

The only mode in which we can judge of the existence of a force is from. 
the effects it produces, and of these effects, that which is the most evident to 



Questions. — Wliat is the supposed ethereal condition of matter, or what are the peculi- 
arities of matter in this condition ? Is matter indestructible ? Is fores indestructible ? 
What reasons induce us to believe that a fores can not b3 destroyed ? 



20 PRINCIPLES OF CHEMISTRY. 

our senses is the power either of producing motion, of arresting it, or of alter- 
ing its direction : whatever is capable of effecting these results is considered 
as a form of force. Motion, therefore, may be considered as the indicator of 
force, and wherever we perceive motion, we may be certain that some force is 
operating. Now it will be found, that in all cases in which work is performed 
— or, to state it in other words, in all cases in which force is exerted and ap- 
parently made to disappear — that it has expended itself either in setting into 
action some other force, or else it has produced a definite and certain amount 
of motion. This motion when used will again give rise to an equal amount 
of the force which originally produced it. For example, we burn coal in the 
air ; the force of affinity causes the particles of coal to unite with the oxygen 
of the air ; the coal changes its form, and a quantity of heat remains, which 
heat represents the chemical force expended. The heat thus developed is now 
ready to do work : it may be employed in converting water into steam, and 
the steam so obtained can, through the medium of machinery, be applied to 
the production of motion. Motion may again be made to produce heat — as 
through friction, for example — and recent experiments seem to show that the 
amount of heat so developed by motion, would, if collected and measured, 
prove to be equal in amount to that which produced the motion. The heat 
produced by motion is generally dissipated and lost for practical purposes, but 
it is not absolutely lost. It has been absorbed, or diffused through space, or 
converted into some other form of force, which in turn takes part in some of 
the great operations of nature, or again ministers to the wants and necessities 
of man. Numerous other facts in support of the view that force, like matter, 
changes but is never destroyed, might be adduced. The subject is one of 
great interest, and has a practical bearing on many of the operations of chem- 
istry. 

25. Classification of Forces, ■ — All the changes which take place in 
matter through the agency of the several forces which act upon it are considered 
under three general divisions, or departments of science, viz., Plrvsics, or 
Natural Philosophy, Animal and Vegetable Physiology, and Chemistry. 

26. Natural Philosophy.— Physics, or Natural Philoso- 
phy, is that department of science which considers generally, 
all those changes and phenomena which are observed to take 
place in matter through the agency of the forces of gravi- 
tation, cohesion, adhesion, capillary attraction, molecular 
repulsion, light, heat, electricity, and magnetism, and 
these several forces have been termed the Physical 
Forces. 

27. Physiology, — Animal and Vegetable Physiology is 



Questions. — Under what three general divisions are the forces which a^t upon matter 
considered? What forces are considered under the department of Natural Philosophy? 
What forces under the department of Animal and Vegetable Physiology? 



INTRODUCTION. 21 

department of science which treats of the changes and 
phenomena observed to take place in matter through the 
agency of the vital force. 

28. Chemistry. — Chemistry is that department of science 
which relates exclusively to all those changes and pheno- 
mena which take place in matter through the agency or 
influence of the force of affinity. 

29. Chemical Action.— Chemical Action is the term used 
to designate all those operations — the result of the force of 
affinity — by which the form, solidity, color, taste, smell, and 
action of substances become changed ; so that new bodies, 
with quite different properties, are formed from the old. 

30. Properties of Matter.— The properties which char- 
acterize material objects in general, may be classed under 
two heads, viz., physical and chemical properties. 

Physical Properties.— The Physical Properties of an ob- 
ject are those by which, it is most readily defined, or dis- 
tinguished from some other object. The form of a body ; its 
condition as a solid, a liquid, or a gas ; its color, hardness, 
tenacity, and its relations to heat and electricity, are ex- 
amples of its physical properties. Physical properties are 
independent of the action which the body exerts upon 
other bodies. 

Chemical Properties. — The Chemical Properties of a 
body are those which relate essentially to its action upon 
other bodies, and to the changes which the body either 
experiences itself, or causes to take place in other bodies 
by contact with them. 

The physical properties of such a substance as sulphur, are, its peculiar odor, 
its yellow color, its brittleness, its crystalline structure, its specific gravity, the 
facility with which it exhibits electrical attraction when rubbed, and the like 
similar qualities, all of which are independent in a great degree of each other, 
and are so distinctive in their character that our senses inform us at once 
that the substance in question is sulphur, and not some other form of matter. 

If we would now enumerate the chemical properties of sulphur, it would 

Questions. — What is chemistry? Define chemical action. Under what two heads 
may the properties of material ohjects be classed ? What are the physical properties 
of a body ? What are chemical properties ? Illustrate the distinction between the 
physical and chemical properties of sulphur. 



22 PRINCIPLES OF CHEMISTRY. 

be necessary to refer to those operations by which the body becomes changed 
and loses its distinctive character — such as the ease with which it takes fire, 
its insolubility in water, and its solubility in oil of turpentine, and the ra- 
pidity with which it unites with iron, silver, copper, and many other of the 
metals. 

Had there been but one kind of matter in the universe, it could have pos- 
sessed only physical properties, and the laws of Natural Philosophy would 
have explained all the phenomena and changes which could possibly have 
taken place in it. As the character or composition of this one form of mat- 
ter, moreover, could not, under the circumstances, have been changed by the 
action of any different substance upon it, it could not have possessed any 
chemical properties, and no idea could have been formed by an intelligent 
being of any such department of knowledge as chemistr} r . 

The connection, however, between Chemistry and Natural Philosophy is 
most intimate ; and all chemical changes are influen?ed to such an extent by 
the action of the physical forces, that a knowledge of the principles of Nat- 
ural Philosophy is requisite for a proper understanding of the nature of 
chemical phenomena. EspeciaUy is this the case as respects the forces mani- 
fested through the agency of Heat, Light, Electricity, and Magnetism ; and a 
brief review of these subjects is generally regarded as a necessary introduction 
to the study of the science of Chemistry. The first part of this work is there- 
fore devoted to a consideration of the nature and action of the physical forces 
so far as they are concerned in producing chemical changes, or in character- 
izing chemical phenomena.* 



CHAPTER I. 

ON THE CONNECTION OF GRAVITY, COHESION, ADHESION, 
AND CAPILLARY ATTRACTION WITH CHEMICAL ACTION. 

SECTION I. 

GRAVITY. 

31. Connection of Gravity with Chemical Phenomena.— 
The influence of the force of gravity on matter is never 

* It has been assumed, in the preparation of this work, that the student is conversant 
with the general principles of Natural Philosophy, and no attempt has therefore been 
made to treat the subjects of Heat, Light, Electricity, and Magnetism in any other than 
a general manner, and with special reference to their connection with chemical pheno- 
mena. 

Questions.— "What connection is there between Natural Philosophy and Chemistry ? 
Is gravity influenced by changes in the condition of matter ? 



WEIGHT. 23 

affected by any change which may take place in the form 
or condition of the matter itself. 

A pound of water is attracted by the influence of gravity toward the cen- 
ter of the earth with a certain degree of force, and as weight is the measure 
of gravity, we express the exact amount of this attractive force, by saying 
that the water weighs a pound. If we deprive this particular quantity of 
water of heat, sufficient to freeze and convert it into ice — a solid — it will 
still weigh a pound ; if we convert the same quantity of water into steam by 
the addition of heat, it will occupy a space seventeen hundred times greater 
than before — yet the steam produced will be attracted by the force of gravity 
equally with the water from which it is derived, and will continue to weigh a 
pound. 

As the action of gravity, therefore, is never suspended, and as the smallest 
particle of matter can not be annihilated by any operation, we are enabled to 
test the accuracy of every chemical process, and ascertain the true composition 
of bodies by proving the weight of the compound to be equal to the weight 
of the substances which produce it. 

32. Use of the Balance. — The balance is to the chemist 
what the compass is to the mariner, and before its intro- 
duction as a means of verifying experiments, the whole 
science of Chemistry was a collection of disconnected and 
separate facts and theories. 

Until within a comparatively recent period it was supposed that common 
air, or gases, did not possess weight ; and this error, which was necessarily 
accompanied with most absurd notions respecting the constitution of air and 
gases, prevailed until the experiment of weighing them was tried, when 
they were found to be attracted by gravity equally with all other kinds of 
matter. 

Less than a hundred years ago it was generally taught and believed that 
when a body was burned, a portion of its substauce was lost. Lavoisier, 
an eminent French philosopher, proved the contrary by carefully burning a 
body, and then weighing all that was left unconsumed by the fire, and all 
the invisible products that escaped. He found, that instead of there being 
a loss of matter, there was a gain, and thus by a simple experiment overthrew 
at once ideas respecting the nature of fire and combustion that had prevailed 
for centuries previous. 

The great distinction, according to Professor Liebig, between Chemistry and 
Natural Philosophy, is that the one weighs and the other measures. 

33. Two Great Systems of Weights.— Two great systems 
of weights are recognized throughout the civilized world in 



Questions.— Give an illustration. What relation does the balance sustain to the opera- 
tions of the chemist? What facts illustrate the use of the balance in effecting chemicaJ 
discoveries ? What two systems of weights are recognized ? 



24 PRINCIPLES OF CHEMISTRY. 

Chemistry and in all other operations. These are known 
as the English and French Systems. 

34. The English System of Weights.— The smallest de- 
nomination of weight made use of in the English System 
(the one generally used in the United States) is a grain. 
The Parliament of England passed a law in 1286, that 
32 grains of wheat ; well dried, should weigh a penny- 
weight. Hence the name grain applied to this measure 
of weight. 

It was afterward ordered that a pennyweight should be divided into only 
24 grains. Grain weights for practical purposes are made by weighing a thin 
plate of metal of uniform thickness, and cutting out, by measurement, such a 
proportion of the whole as will weigh one grain. In a like manner, weights 
may be obtained for chemical purposes which weigh only the 1,000th part of 
a grain. 

Seven thousand grains constitute a pound avoirdupois, 
and from this pound all measures of capacity have been 
derived by Act of the English Parliament. 

Thus a standard gallon is by law as much distilled water as will weigh ten 
pounds, or 70,000 grains; and a measure holding exactly this quantity of 
water is a gallon measure. By subdividing the gallon we obtain smaller 
measures, quarts, pints, etc. 

35. French System of Weights, —The French System of 
Weights is constructed on a different plan, and is distin- 
guished for its great simplicity — all its divisions being 
made by ten. It is, therefore, sometimes called the deci- 
mal system. 

On the continent of Europe this system of weights is almost universally 
adopted for all scientific operations, and is gradually beiug introduced into 
England and the United States. It is, therefore, highly important that the 
principles upon which it is based should be understood. 

The basis of the French System is an invariable dimen- 
sion of the globe, viz., a fourth part of the earth's merid- 
ian, or a fourth part of a circle passing round the earth 
(lengthwise), and intersecting at the poles. 



Questions — What is the smallest weight recognized in the English System ? What 
is a pound avoirdupois? How are measures of capacity derived from measures of 
weight ? What is an English gallon ? What is the distinguishing peculiarity of the 
Trench system of weights ? Where is the French system used ? What is its basis 9 



WEIGHT, 



25 



The circle N E S TV, Fig. 6, represents a 
meridian of the earth ; and a fourth part of 
th's circle, or the distance N E, constitutes 
the dimension on which the French System 
is founded. 

This distance, which was accu- 
rately measured, is divided into 
ten million equal parts ; and a 
single ten millionth part adopted 
as a measure of length, and called 
a metre. 

A metre is about three feet and a quarter in length, or about thirty-nine 
English inches. By multiplying or dividing the metre by ten, all the larger 
and smaller measures of length are obtained. For indicating measures smaller 
than a metre, Latin terms are used ; for indicating measures larger than a 
metre, Greek terms. Thus — 




Smaller Measures. 
Metre. 

Decimetre = l-10th metre. 
Centimetre= 1-1 00th metre. 
Millimetre =l-1000th metre. 



Larger Measures. 
Metre. 

Decametre = 10 metres. 
Hectometre= 100 metres. 
Kilometre = 1,000 metres. 
Myriarnetre=10,000 metres. 



The system of weights was formed from measures of length in the follow- 
ing manner. A box, in the form of a cube, was taken, measuring one centi- 
metre in every direction. This, filled with distilled water at its greatest 
density (at a temperature of 39° Fahrenheit's thermometer), was taken as the 
unit of the decimal weights, and called a gramme* — a quantity equal to about 
fifteen English grains. The gramme, multiplied and divided by ten, gives all 
the other larger or smaller weights. Thus — 

Smaller Weights. Larger Weights. 

Gramme. 

Decigramme =■ l-10th gramme. 

Centigramme= 1-1 00th gramme. 

Milligramme =1 -1,000th gramme. 



Gramme. 

Decagramme =» 10 grammes. 
IIectogramme=i 100 grammes. 
Kilogramme = 1,000 grammes. 
Myriagramme==l 0,000 grammes. 



The kilogramme corresponds in its use in all commercial transactions with 
the English pound. Its weight is equal to about 2£ pounds avoirdupois,. 



Pronounced Gram. 



Questions. — What is the Metre of the French system? How are the larger and 
smaller measures of length derived from the Metre ? How is the system of weights de- 
rived from the measures of length ? What is a Kilogramme ? 



26 



PRINCIPLES OF CHEMISTRY. 



Fig. T. 




36. Construction of 

I lie Balance. — The bal- 
ance used for all deli- 
cate chemical experi- 
ments is constructed in 
the most perfect man- 
ner. The point of sup- 
port of the beam (see Fig. 7) is a wedge of hardened 
steel with a sharp, knife-like edge, which rests upon a flat 
plate of p>olished agate. The points of support of the two 
scale-pans are often constructed in a similar manner. 

In all nice experiments the balance must be screened from currents of air, 
and the bodies weighed must have nearly the same temperature as that of the 
surrounding atmosphere — otherwise currents of air, ascending and descending, 
will be produced, which will impair the accuracy of the weight. 

Balances are at the present time constructed for chemical operations, so 
delicate and exact, that they are able to indicate the weight of a thousandth 
part of a grain. 

For the experiments described in this book, a common apothecaries' balance 
i3 all that is requisite. 

31. Weight Compared with Bulk.— If equal bulks of matter of 
different kinds be compared together, they will be found to differ greatly in 
weight. Platinum, the heaviest body known, is upward of 200,000 times as 
dense, bulk for bulk, as hydrogen. 

Specific Gravity. — The specific gravity, or specific weight 
of a body, is its weight as compared with the weight of 
an equal bulk of some other substance, assumed as the 
standard of comparison. 

Absolute Weight. — The absolute weight of a body is the 
weight of its entire mass, considered without any reference 
to its bulk, or volume. 

The weight of a body, as determined by the ordinary process of weighing, 
is its absolute weight. 

Pure water, at a temperature of 60° Fahrenheit," has been selected as the 
standard for comparing the weights of equal bulks of different solids and 
liquids ; and common air, dry, and at a temperature of G0° Fahrenheit, and 



Questions. — What are the peculiarities of the balance as used for chemical investiga- 
tions '? What precautions are to be observed in nice experiments ? How do equal bulks 
of different substances compare? "What is specific gravity, or specific weight? W r hat 
is absolute weight ? 



WEIGHT, 



2T 



Fig. 8. 



30 inches pressure of the barometer, as the standard for comparing the weights 
of equal volumes of different gases and vapors. 

Attention is given to temperature, and to the pressure of the atmosphere, 
because the bulk of all substances sensibly varies with changes in these con- 
ditions. 

Water having been selected as the standard of comparison the question to 
be settled in the determination of the specilic gravity of a body is simply this 
— how much heavier or lighter is a given bulk of a substance, than an equal 
bulk of water ? The solution of the problem may be found by the following 
general rule : 

38. Weigh first the body in air, and afterward weigh it 
when suspended in water. It will be observed to weigh 
less in water than in air. Subtract the weight in water 
from the weight in air ; and divide the weight in air by 
the difference ; the quotient will be the specific gravity 
required. 

This rule is based upon the fact, that 
a solid when weighed in water loses 
weight equal to the water it displaces ; 
and the bulk of the water displaced is 
exactly equal to its own. 

Suppose a piece of gold weighs in tho 
air 19 grains, and in water 18 grains; 
the loss of weight in water will be 1 ; 
19-^-1=19, the specific gravity of gold. 

Fig. 8 represents the arrangement of 
the balance for taking specific gravities, 
and the manner of suspending the body 
in water from the scale-pan, or beam, 
by means of a fine thread, or hair. 

39. The specific gravity of 
liquids is easily determined in 
the following manner. A bottle capable of holding ex- 
actly 1,000 grains of distilled water is obtained, filled with 
water, and balanced upon the scales. Tho water is then 
removed, and its place supplied with the liquid whose spe- 
cific gravity we wish to determine, and the bottle and con- 
tents again weighed. The weight of the fluid, divided by 
the weight of the water, gives the specific gravity required. 




Questions.— Wh at are the standards of specific gravity ? How may the specific gravity 
of solids be determined ? Upon what principle is this rule founded ? How may the specific 
gravity of liquids be determined ? 



28 



PRINCIPLES OF CHEMISTRY. 



Fig. 9. 



Thus, a bottle holding 1,000 grains of distilled water, will hold 1,845 grains 
of sulphuric acid ; 1,845-4-1,000=1,845, the speciQc gravity of sulphuric acid ; 
or this liquid is 1.845 times heavier than an equal bulk of water. 

40. The specific gravity of liquids may also be obtained without the aid of 
a balance, by means of an instrument called the Hydrometer. 

The Hydro'meter — This consistsof a hol- 
low glass tube, on the lower part of which 
a spherical bulb is blown, the latter being 
filled with a suitable quantity of small 
shot, or quicksilver, in order to cause it 
to float in a vertical position. The upper 
part of the tube contains a scale gradu- 
ated into suitable divisions. (See Fig. 9.) 

It is obvious that the hydrometer will sink to a greater 
or less depth in different liquids ; deeper in the lighter 
ones, or those of small specific gravity, and not so deep 
in those which are denser, or which have great specific 
gravity. The specific gravity of a liquid may, there- 
fore, be estimated by the number of divisions on the 
scale which remain above the surface of the liquid. 
Tables are constructed, so that, by their aid, when the 
number on the scale at which the hydrometer floats in a given liquid is de- 
termined by experiment, the specific gravity is expressed by figures in a col- 
umn directly opposite that number in the table. 

The liquid whose specific gravity is to be determined, is usually, for conve- 
nience, placed in a narrow vessel or jar (see Fig. 9), and the zero point on the 
scale of the hydrometer is always placed at that point where the instrument 
will float in pure water. The numbers on the scale read either up or down, 
according as the liquid to be tested is either heavier or lighter than water. 

For the testing of alcohol and spirituous liquors, a particular form of hy- 
drometer is used, called the " alcoholo'meter." This is so graduated as to 
indicate the number of parts of pure alcohol in a hundred of liquid ; — perfectly 
pure, or, as it is called, " absolute" alcohol, being 100, and pure water 1. 

In the arts, a French hydro'meter, known as Beaum&s, and an English in- 
strument known as Twaddell's, so called from their makers, are much used. 
Dealers and manufacturers of spirituous liquors, syrups, oils, leys for soap- 
making, etc., in buying, selling, or compounding, are accustomed to indicate 
the strength or quality of their products, by saying that they stand at so many 
degrees Beaume, or Twaddell. 




Quk6tions. — What is a hydrometer? Upon what principle may the specific gravity 
of a liquid be determined by the hydrometer ? How is the hydrometer graduated ? 
What is an alcoholometer ? What are the instruments known as Beaume and Twad- 
dell? 



COHESION. 29 

The practical value of the hydrometer in the arts as a labor-saving inven- 
tion, is very great. The soap-maker, by dipping the instrument into his ley, 
and noticing the point at which it floats, knows at once by experience whether 
it is of sufficient strength to convert his grease into soap ; the salt-boiler, by 
a like observation, is enabled to judge how long his brine must be boiled be- 
fore salt will deposit at the bottom of his kettles ; and the bleacher has in a 
like manner a sure check against the use of bleaching liquors of strength suf- 
ficient to damage his fabrics. So in very many other industrial processes also 
the hydrometer is equally useful. 

41. Specific Gravity of Gases. — In principle, the method 
of determining the specific gravity of gases is the same 
as that used in the case of solids. A flask, or globe, is 
first weighed empty, then when filled with air, and a third 
time, when the gas whose specific gravity is sought for, 
has been substituted for air. The difference between these 
respective weights furnishes the data for calculating the 
specific gravity required. 

42. The specific gravity of a body constitutes one of its most important and 
distinguishing physical characteristics. Thus, for instance, the mineral known 
as iron pyri'tes resembles gold in color so closely, that it is often mistaken 
by the unskilled for that metal. It may, however, be at once distinguished 
from gold by the difference in specific gravity, an equal bulk of gold being 
nearly four times as heavy. 

SECTION II. 

COHESION. 

43. Cohesion and Chemical Action,— The force with 
which like particles of matter are held together by the in- 
fluence of cohesion, or what is termed the " strength of ma- 
terials/' although of great importance in all the operations 
of the mechanic, the engineer, and the architect, has com- 
paratively little to do with Chemistry. Variations, how- 
ever, in the cohesion and aggregation of the particles of 
a particular substance, modify, to a considerable extent, the 
nature and rapidity of chemical action upon it. 

Thus gunpowder, for example, when in the form of a hard cake, or as fine 
dust, burns comparatively slowly, as in what is termed a slow match, or fuse ; 

Questions. — Explain the practical value of the hydrometer as a labor-saving expedient. 
How may the specific gravity of a gas be determined ? Is the specific gravity of a sub- 
stance one of its important characteristics ? What is the relation of the force of cohesion 
to chemical action ? 



«5U PRINCIPLES OF CHEMISTRY. 

but in the form of fine grains, each portion quickly ignites, and an almost in- 
stantaneous explosion occurs. 

As a general rule, the cohesion of a body diminishes as 
its temperature increases. A heated liquid forms smaller 
drops than a cold one. Sulphur, of all bodies, is an ex- 
ception to this rule, its consistency increasing, after melt- 
ing, as its temperature rises. 

In liquids, notwithstanding the freedom with which their particles glide 
over each other, there still exists an appreciable amount of cohesion. This is 
shown by the fact that every detached drop of a liquid, as a dew-drop upon 
a leaf, always assumes a rounded form — a globe or sphere being the figure 
which will contain the greatest amount of matter within a given surface. 

This influence of cohesion is beautifully shown in -the case of two liquids 
which do not mix with each other, but which have precisely the same specific 
gravity, as is the case with oil and alcohol of a certain degree of dilution. 
If a little oil be poured into weak alcohol, it remains suspended within it in 
the form of a perfect spherical mass.* 

44. Limpid and Vis'cous Liquids.— Liquids, according to 
the difference of cohesive force which exists among their 
particles, have received the distinctive names of limjpid 
and vis'cous. 

Limpid Liquids are those which, like ether, alcohol, etc., 
display great mobility of their particles. Bubbles pro- 
duced in such liquids by agitation, quickly rise to the sur- 
face, break, and disappear. 

Vis'cous L i q u i d s are those in which the particles are held 
together so strongly, by the force of cohesion, that they 
move sluggishly upon one another. Oil, syrup, gum- 
water, etc., are examples of viscous liquids. 



* This experiment may be successfully and easily performed by the teacher in the fol- 
lowing manner : — Oil will float upon the surface of water, but will sink to the bottom of 
6trong alcohol ; if we, therefore, pour a portion of alcohol into a glass, and put in a glo- 
bule of oil (olive oil is preferable), the spirit will float above it, and the oil will have the 
form of a flattened spheroid. If we now add a little water, and mix it carefully with the 
Bpirit without breaking the floating mass of the oil, it will be seen to swim higher up in 
the spirituous medium and present less flatness, and by continuing to carefully add water, 
we may at last bring the oil to the very center of the fluid, where it will assume the form 
of a perfect sphere. 

Questions. — What relation exists between cohesion and temperature ? Does the cohe- 
sive force influence the particles of liquids ? Why is a dew-drop spherical in shape ? 
What experiment illustrates the cohesion of liquids ? Into what two classes may liquids 
be divided ? What is a limpid liquid ? What is a viscous liquid ? 



COHESION. 31 

45. Variations of Cohesion in Solids.— Those proper- 
ties of solid bodies which we denominate hardness, soft- 
ness, brittleness, malleability, and ductility, are occasioned 
by variations of the cohesive force. The cause of these va- 
riations, or the reason why one metal should be malleable 
and another ductile, or why the same substances should 
possess, under different circumstances, different degrees of 
hardness, is not fully understood. 

The most trifling variations in the external circumstances to which a body 
is subjected, will often produce the most extraordinary differences in its hard- 
ness, brittleness, ductility, and malleability. A piece of steel slowly cooled 
from a red heat is soft, and may be easily cut with a file, or stamped with a 
die ; but the same piece of steel, if heated to redness and suddenly cooled, 
becomes extremely hard, and as brittle as glass. Gold is one of the most 
ductile of metals, but if a mass of melted rcIJ. be exposed to the mere fames 
of antimony, it loses its ductility altogether :;: 

46. Hardness. — The hardness of a body is measured by 
its power of scratching other substances. 

The variations in the degree of hardness presented by 
different bodies, often furnish the mineralogist and chem- 
ist with a valuable physical test, by which they are en- 
abled to distinguish one mineral from another. For the 
purpose of facilitating such comparisons a table has been 
constructed, by taking ten well-known minerals, and ar- 
ranging them in such a way that each is scratched by the 
one that follows it. Such a table is known as the Scale 
of Hardness ; and by comparing any unknown mineral 
with this scale, its comparative degree of hardness may 
be at once determined. 

For example, suppose a body neither to scratch nor to be scratched by 
pure quartz, or rock crystal, which is No. 1 of the table, its hardness is said 
to be 7 ; if, however, it should scratch quartz, and not scratch the topaz, 
which is No. 8 of the table, its hardness would be said to be between 7 and 
8. Yery many different minerals have the same external appearance, and by 
the sight alone can not be distinguished from each other ; but by the employ - 

* See Crystallization. 

Questions — What physical properties of bodies are due to variations of the cohesive 
force ? How is the hardness of a body measured ? What is the scale of hardnpss ? 
How is the scale of hardness used, and w hat are its advantages in determining the char- 
acter of minerals ? 



32 PRINCIPLES OF CHEMISTRY. 

ment of this test, a difference in their physical or chemical composition may 
be at once recognized.* 

SECTION III. 

ADHESION AND CAPILLARY ATTRACTION. 

47. Adhesion and Chemical Action.— The force of ad- 
'nesion is exerted between substances in every form ©r 
condition. When it occurs between solids, it is the prin- 
cipal cause of that resistance to motion which is termed 
friction. 

As a general rule ; friction is greater between surfaces 
of the same substances than between those of unlike sub- 
stances. Thus an iron axle moving in an iron box or 
socket, experiences a greater amount of friction than if 
revolving in a brass socket. 

We reduce the amount of friction between two surfaces by interposing some 
substances, like grease, oil, black-lead, etc., the particles of which have very 
little cohesion. 

The valuable properties of cements and mortars depend 
entirely upon the operation of the force of adhesion. The 
fact, also, that different kinds of cement are required for 
joining together different materials, proves that adhesion 
acts with varying degrees of force between different kinds 
of matter. 

Thus, glue or gum may be used for joining pieces of paper or wood, but 



* The following is the scale of hardness generally adopted : — 

1. Talc. 6. Feldspar. 

2. Compact gypsum. 7. Limpid quartz. 

3. Calcareous spar. 8. Topaz. 

4. Fluor spar. 9. Sapphire, or Corundum. 

5. Apatite (phosphate of lime). 10. Diamond. 

Each of these minerals is harder than those which precede it, and is softer than any 
which follow it. 

Teachers and pupils can, with the exception of No. 10, the diamond, easily obtain tho 
materials necessary to construct the scale of hardness as above given. It may also he ob- 
tained, put up in a neat box, of most philosophical instruments dealers, at a trifling ex- 
pense. 

Questions.— In what manner is the force of adhesion exerted ? What is friction ? 
Under what circumstances is friction the greatest ? How may friction be diminished ? To 
what are the valuable properties of cements and mortars due ? What facts prove the 
varying force of adhesion? 



ADHESION AND CAPILLARY ATTRACTION. 33 

they will not answer for cementing glass or china ; while for the union of 
marble, brick, or stone, a cement containing lime is required. 

Generally, the force of adhesion is inferior in strength 
to the force of cohesion : but in some instances the oppo- 
site is true. 

Thus, in detaching glue from the surface of wood, it not unfrequently hap- 
pens that portions of the wood are torn off by the glue, on account of the 
force of adhesion between the two bodies proving stronger than the force of 
cohesion between the particles of the wood. 

The property of water to adhere to solid surfaces and wet them, and the 
rapid diffusion of a drop of oil over the surface of water, are illustrations of 
the force of adhesion between solids and liquids, and between different 
liquids. 

Some experiments seem to show that the force of adhesion may even over- 
come the force of affinity under some circumstances. Thus, when vinegar 
is filtered through pure quartz sand, the first portion that runs through is de- 
prived of nearly all its acid, and the vinegar will not pass through unchanged 
until the sand has become charged with acid. 

48. Surface Action.— As adhesion takes place solely be- 
tween the surfaces of bodies, it is evident that whatever 
circumstances affect surface must essentially influence the 
exertion of the force of adhesion. It has accordingly been 
found that by minutely subdividing a body, and thus in- 
creasing its extent of surface, we generally increase the 
effect of adhesion. 

A cubic inch of matter cut into little cubes, each l-2400th of an inch on 
the edge, will exhibit a surface of exactly 100 square feet. 

All pulverized bodies, by reason of their great extent of surface, attract 
moisture, or the vapor of water, and also air, so that by exposure to the at- 
mosphere they increase in weight to a considerable extent. 

A most striking illustration of the fact that extent of surface facilitates the 
action of adhesion is found in the case of charcoal. "When wood is heated 
apart from the air, certain portions of matter which compose its structure are 
driven off by the action of the heat, and the charcoal, which remains behind, 
is left full of little pores, or openings. In this way an enormous extent of 
surface is acquired, so much so, that a cubic inch of good charcoal is esti- 
mated to have a surface of at least a hundred square feet. By reason of such 
an extended surface, the effect of the force of adhesion existing between char- 



Questions — Why is not glue suitable for cementing glass or china ? Does the force of 
adhesion ever prove superirr to the force of cohesion? What are illustrations of adhe- 
sion between solids and liquids ? What influence has surface upon adhesion ? Why do 
most pulverized substances attract moisture ? How does charcoal illustrate the influence 
of surface upon the force of adhesion ? 



34 PRINCIPLES OF CHEMISTRY. 

coal and various liquids and gases is greatly increased. Thus, it has been 
found that freshly-burned charcoal is capable, through the force of adhesion 
alone, of absorbing or condensing upon its surface from 80 to 90 times its own 
bulk of certain gases ; and that it absorbs, when exposed to moist air, so much 
water, as to increase in weight by nearly one fifth. 

All coloring matters of vegetable or animal origin, and many other sub- 
stances, have likewise the property of adhering to charcoal — a circumstance 
which has been turned to great practical advantage in the arts. 

Other substances beside charcoal, exert, by reason of their peculiar ex- 
tension of surface, a similar influence on the force of adhesion. Metallic 
platinum, finely divided, is even more remarkable in its effects than charcoal, 
and is capable of absorbing eight hundred times its bulk of oxygen gas. 
This oxygen must be contained within it in a state of condensation very 
like that of a liquid. In a like manner, every porous body attracts, through 
the force of adhesion, air and moisture to a greater or less degree, the action 
of the force being proportioned to the extent . of the porosity, or the surface 
exposed. A field whose soil is finely divided and kept porous by a high state 
of cultivation, suffers less from drought than one similarly situated which is 
partially or wholly uncultivated. It is not improbable, also, that plants are 
assisted in obtaining nutriment from the air, through the influence of an ad- 
hesive force acting between the surfaces of their leaves and the constituents 
of the atmosphere. 

49. Capillary Attraction . — T he phe nomena produced by 
the agency of the force of capillary attraction are similar 
in character to those produced by the force of adhesion. 
Indeed, according to some authorities, capillary attraction 
is merely a variety of adhesion.* The fact, however, that 
capillary attraction both elevates and depresses the sur- 
faces of liquids, seems to prove that there are essential 
differences between these two forces. 

The two distinguishing manifestations of capillary attraction may be clearly 
illustrated by the following experiments : — 

If a liquid be poured into a vessel, as water in glass, whose sides are of such 
a nature as to be wetted by it, the liquid will be elevated above the general 



* According to the latest and best sustained hypothesis on this subject, the phenomena 
of capillary attraction are due not only to an adhesive attraction between the liquid and 
the solid, but also to a contractile force existing on the free surface of every liquid, and 
which is increased or diminished in a given direction by the convexity or concavity of this 
surface. 



Questions. — What other facts illustrate the influence of surface action ? Do the phe- 
nomena of capillary attraction resemble those of adhesion ? How may the two distin- 
guishing manifestations of capillary force be exhibited ? 





ADHESION AND CAPILLARY ATTRACTION. 35 

level of its surface at the points where it touches the 
sides of the vessel. This is shown in Fig. 10. 

If, however, the liquid is poured into a vessel whose 
sides are of such a nature that they are not wetted by 
it, as in the case of quicksilver in glass vessel, then the 
liquid will be depressed below the general level of its 
surface at the points where it comes in contact with 
*" the sides of the vessel. This is shown in Fig. 11. 
In like manner, if we plunge a small tube of glass into 
water, the liquid will rise in it above the general level ; 
but if we plunge it into mercury, the liquid will be de- 
pressed below the general level, or will not enter the 
tube at all. 

It has been proved by experiment, that water, through 
the force of capillary attraction, can be made to pass 
through a crevice the width of which is less than one 
half of the millionth of an iuch. 

Notwithstanding the force which capillary attraction 
exerts to cause liquids to rise, or pass into tubes of small 
diameter, it can not of itself establish a flowage, or con- 
tinuous current. If, however, a part of the liquid be re- 
moved from the end of the capillary tube by evaporation, 
or other agency, an additional portion will be pushed for- 
ward by capillary force to supply its place, and in this 
way a current may be established. 

An illustration of this is seen in the case of an oil-lamp, the witk cf which 
may be regarded as a bundle of capillary tubes. So long as the lamp remains 
uniighted, the wick, although full of oil never overflows; but when the lamp 
is lighted, and the oil burned off from the top, a current is at once created. 

Different liquids do not appear to be equally suscept- 
ible to the action of the capillary force. Thus, if we rep- 
resent the height to which water will ascend in a capillary 
tube by 100, the height to which alcohol will ascend in the 
same tube will be only 40, and a solution of common salt 
in water, 88. 

50. Filtration. — The process of filtration, or the separa- 
tion of impurities from liquids by straining, or filtering 
them through some porous substance, is the result of the 



Questions. — Can capillary force produce a current of liquid through the pores of a sub- 
stance ? Are all liquids elevated to the same height in capillary tubes ? Upon what does 
Uie process of nitration depend ?. 



36 



PRINCIPLES OF CHEMISTRY. 



action of capillary force. The pores, or interstices which 
exist between the particles of the substance used as a 
filter, are really little capillary tubes through which the 
liquid passes, leaving the solid impurities contained in it 
behind. 

"When a drop of ink, or chocolate falls upon cloth, or blotting-paper, it pro- 
duces a dark central spot surrounded by a circle of a paler colored liquid. 
This is due to the fact that the particles of the liquid only are enabled to dif- 
fuse themselves, or "spread," as it is termed, through the pores of the ma- 
terial. That appearance of the skin which accompanies a contusion, and is 
termed " black and blue," is a similar phenomenon — the result of a separation 
of the coloring and denser matters of the blood from the watery portions, by 
a process of filtration through the pores of the tissues. 

In chemical operations, coarse sand, or cloth, is sometimes used to form 
filters, but most generally a variety of porous, or unsized paper (blotting- 
paper), is employed. "Writing-paper can not be used for filtration, as its pores 
are filled up with glue, or starch. For a like reason, ink does not " spread" 
on this kind of paper. 

A paper filter is prepared by folding a circular piece of unsized paper into 
the form of a quadrant, which is then opened to form a cone. It is generally 
fitted into a funnel, which is supported upon a stand. (See Fig. 12.) 

FiG. 12. 





A filtered liquid is termed & filtrate. 
51. En'dosmosis.— When two liquids which are capable 
of mixing with each other, as alcohol and water, are sep- 



Quebtionb.— Why can not " sized," or writing-paper, be used for filtration? How is a 
paper filter prepared ? What is a filtrate ? What is endosmosis ? 



ADHESION AND CAPILLARY ATTRACTION. 



37 



arated by a substance, or partition which is porous, each 
will pass through the partition in opposite directions, in 
order to mix with the other. The exchange, however, 
always takes place in unequal proportions, so that the 
volume of one liquid increases while that of the other 
diminishes. This phenomenon is known by the name 
of Endosmosis. 

The name Endosmose, derived from the Greek, and signifying "to go in" 
is applied to designate the stronger current, because it penetrates into the 
opposite liquid ; while the name Exosmose, which signifies " to go out," is ap- 
plied to the weaker current. 

The phenomena of endosmosis may be illustrated by the following ex- 
periments : — If some alcohol be placed in a 
bladder, the neck of which is tightly tied, 
and the bladder be sunk in a vessel of 
water, the water will pass into the bladder 
to such an extent as to distend it, even to 
bursting. 

The same result may be also shown more 
effectively by means of an instrument called 
the endosmometer. This consists (see Fig. 
13) of a bladder filled with alcohol, which 
is tightly fastened to one end of a tube and 
inserted in a vessel of water — the tube being 
sustained in a vertical position. As the 
water introduces itself through the pores 
of the bladder the liquid rises in the glass 
tube, and, if the action be continued suffi- 
ciently long, it will rise to the top and over- 
flow. Such an instrument as this may be 
kept in operation a long time, the liquid 
flowing continually over the top of the tube. 
At the same time that the water is passing 
from without into the bladder to reach the 
alcohol, a very small quantity of alcohol is 
passing through the bladder in a contrary 
direction to reach the water. 
The explanation of this phenomenon of endosmosis is as follows : — The 
pores of the bladder, or any other like substance, are merely short capillary 
tubes through which the water passes by the force of capillary attraction. 
If the bladder be distended with air and sunk under water, the water will fill 
the tubes, but will not discharge itself in the interior, since capillary force 




Questions. — What is the origin and derivation of the name ? What experiments illus- 
trate the phenomena of endosmosis ? How is endosmosis explained ? 



38 PEINCIPLES OF CHEMISTKY. 

alone can not establish a continuous movement. But when the bladder is 
filled with alcohol, the case is different ; since the alcohol dissolves away the 
water as fast as it reaches the interior, and thus produces a constant and rapid 
current. 

The reason that the water passes in more rapidly than the alcohol passes 
out, is due to the fact that the water adheres more strongly to the walls of 
the bladder than the alcohol does — and of any two liquids, that which most 
freely wets the porous dividing partition will always flow in the stronger 
current. 

Any two liquids may be used to exhibit the action of endosmosis, provided 
that they have different degrees of attraction for the bladder, and a strong 
tendency to mix with each other. Thus, in the above experiment a solution 
of gum, of salt, or of sugar in water, might have been substituted in place of 
the alcohol. 

Very thin plates of slate-stone, or of baked clay, may be also used in place 
of a bladder, or membrane. 

The forco with which a liquid will pass through a pore 
to mingle with another liquid beyond is very great — oc- 
curring in some instances in opposition to a pressure of 
from forty to seventy pounds upon a square inch. 

An India-rubber bottle, filled with sulphuric ether, and carefully closed, 
will gradually empty itself if placed in either alcohol or water. If filled with 
alcohol, it distends itself in ether, but empties itself in water ; if filled with 
water, it distends when placed in either alcohol or ether. 

If a bladder containing equal parts of alcohol and water be hung up in the 
air, the water will gradually escape through the membrane, leaving the strong 
spirit behind. In the same manner, if strong alcohol be placed in a wine- 
glass covered with porous paper, the water contained in it escapes, and the 
spirit increases in strength. 

Enclosmotic action exercises an important influence in 
many of the operations of chemistry 3 and of animal and 
vegetable life. 

The power which plants possess of absorbing nutritive matter from the 
soil, through the delicate fibers of their roots, is supposed to be due in part 
to the action of endosmosis. 

All nutriment taken up by the organs of the body, reaches the interior of 
the system by passing through animal membranes in the fluid state. TL© 
food we eat passes from the mouth through the throat to the stomach. The 
structure of the membranes which line the throat is such, that fluids can not 
pass through them, but the walls cf the stomach and of the intestines are 

Questions. — What determines the rapidity of the two currents in endosmotic action ? 
Under what circumstances will different liquids exert this action ? Does endosmosis 
exert an influence upon chemical and physiological operations ? What are illustrations 
of this fact ? 



ADHESION AND CAPILLARY ATTRACTION 



39 



Fig. 14. 



differently constituted, and at these points endosmotic action is continually 
and energetically going on within us. 

Endosmotic action takes place between different gasga. 
much, more powerfully than between different liquids. No 
matter what the thickness, or thinness of the porous sub- 
stance separating tw r o gases may be, currents are estab- 
lished through it, until the media on both sides have the 
same chemical composition. 

The following simple experiment shows this action : — If we tie over the 
mouth of a glass jar filled with carbonic acid gas, a thin sheet of India rubber, 
and expose the whole to the air, the car- 
bonic acid will pass out so fast that the 
cover will be depressed by the external 
pressure of the atmosphere almost to the 
bottom of the jar. (See <z, Fig. 14.) If, 
on the contrary, we fill the jar with air, 
and place it in an atmosphere of carbonic 
acid, the movement takes place in an 
opposite direction — a little air flows out 
of the bottle into the carbonic acid, but so 
large a quantity of the gas passes the 
opposite way, that the India rubber swells 
out, and caps the bottle like a dome. (See 
6, Fig. 14.) 

52. Diffusion of Gases.— Connected with this subject 
is another interesting class of phenomena, known as the 
diffusion of gases. 

When two liquids which are wanting in any attraction 
for each other, as oil and water, are mixed together, they 
separate after standing at rest, and arrange themselves 
according to their specific gravities, the heaviest at the 
bottom and the lightest at the top. If, however, a 
light and heavy gas are once mixed together, no sepa- 
ration takes place, but the two remain permanently in- 
termingled. 

It has also been found that every gas, or gaseous mix- 
ture, possesses the power of diffusing itself equally 




Questions Does endosmotic action take place between different gases ? What are 

illustrations of it ? What is meant by the diffusion of gases ? How is each gas affected 
es regards the presence cf another gas ? 



40 



PRINCIPLES OF CHEMISTRY. 



through every other gas with which it is brought in con- 
tact, and this, too, in opposition to the action of their 
weight, or gravity. 

Fig. 15. Tbus ' carbonic acid g as is twenty-two times heavier than 

^ ^ hydrogen gas, but if a jar filled with hydrogen be placed with 
its mouth downward over the mouth of a jar filled with car- 
bonic acid, as shown in Fig. 15, the two will diffuse them- 
ijjljjy selves so completely that in a few moments each jar will con- 
tain equal quantities of both gases. 

Each gas appears to act as void, or 
empty space for another, or, in other words, 
it spreads, or expands into the space occu- 
pied by another gas, as if it were a vacuum. 
The same law applies also to vapors. 

Thus, as much steam can be forced into a space filled with 
dry air, as into a space absolutely devoid of air, or any other 
substance. 

This force, or law, regulating the diffusion of gases, is one 
of great practical importance in the operations of nature, and 
I r^r i- . . j is often referred to as a most remarkable evidence of design 
on the part of the Creator. Thus, carbonic acid, which is a 
deadly poison when inhaled, is one and a half times heavier than common 
air. The atmosphere contains about one part in two thousand of this gas, 
uniformly diffused through it — the same quantity being present in air col- 
lected on the tops of the highest mountains and on the level surface of the 
earth. If the law which produces such a complete diffusion were suspended, 
this heavy gas would accumulate under the influence of gravitation as a bed 
or layer in the lower part of the atmosphere, and render the immediate sur- 
face of the earth uninhabitable. 

By reason of this same law of diffusion, the carbonic acid gas which is 
abundantly formed in every process of combustion and in respiration, and the 
noxious gases discharged from sewers, and from all decaying matter, are si- 
lently and speedily dispersed, and prevented from accumulating. 

The equable diffusion of vapor of water through the atmosphere, in ac- 
cordance with the same law, is no less important than the diffusion of gases. 
But for such diffusion, the whole surface of the earth would have assumed 
the condition of an arid desert. Water is 800 times more dense than air, yet 
the particles of water in the form of vapor ascend into the atmosphere, and 
diffusing themselves everywhere throughout its substance, give rise to the 
phenomena of dew and rain. 

It is through the operation of this principle, also, that we are enabled to 

Questions. — What practical bearing has the law of diffusion upon the constitution of 
the atmosphere "? Wha.t upon the condition of the earth's surface ? How is it that we 
are enabled to perceive the odor of volatile substances at a distance ? 



ADHESION AND CAPILLARY ATTRACTION. 41 

perceive and enjoy at a distance the fragrant odors which arise from volatile 
substances ; and were its action suspended, the sense of smell would be nearly 
unknown to us. 

53. Diffusion of Liquids.— Liquids of different densities, 
which are susceptible of mixing, will, when brought in 
contact, gradually become intermingled, by a law some- 
what resembling that which governs the diffusion of gases. 

Thus, if pure water be carefully poured upon a strong- solution of salt or of 
sugar, the lighter fluid will at first float upon the surface of the heavier ; but 
after a time the two will mingle together more or less uniformly. In like 
manner, a drop of ink, or other similar coloring matter, will diffuse itself 
through a large quantity of water. 

54. Solution.— When the adhesion between the parti- 
cles of a solid and those of a liquid is more powerful than 
the force of. cohesion which binds together the particles of 
the solid, the power of cohesion will be entirely overcome, 
or suspended, and the substance is said to dissolve, or 
undergo solution in the liquid. In this way sugar or salt 
dissolves in water, rosin or camphor in alcohol, and lead 
or silver in mercury. 

A body is said to be insoluble when the adhesive force 
exerted by a liquid upon its particles, is not strong 
enough to overcome the cohesive force which binds them 
together. 

Any thing which weakens the force of cohesion in a solid favors solution. 
Thus, if a substance be reduced to a powder, it dissolves more quickly, both 
from the larger extent of surface which it exposes to the action of the liquid, 
and from the partial destruction of cohesion between its particles. In the 
same way heat, by diminishing the force of cohesion, generally promotes the 
process of solution. Some substances, however, as lime, for example, dis- 
solve more freely in cold than in warm water. 

55. Saturation. — When a liquid has dissolved as much 
of a solid as it is capable of doing, it is said to be satu- 
rated. W^hen this occurs, the force of adhesion between 
the liquid and the solid becomes reduced to an equality 
with the force of cohesion between the particles of the 
solid, and the act of solution ceases. 

Qttestioxs. — What is understood by the diffusion of liquids ? What are illustrations of 
liquid diffusion ? What is solution ? When is a body said to be insoluble ? What cir- 
cumstances favor the solution of a solid ? What is saturation ? 



42 PRINCIPLES OF CHEMISTRY. 

56. Precipitation. — When a solid body dissolves in a 
liquid, the property of cohesion is not destroyed, but 
merely overcome, or suspended by the superior force of 
adhesion. If this latter force is in turn weakened, or 
overcome, the force of cohesion acquires an ascendancy, 
and the particles in solution unite again to form a solid. 
A solid thus reproduced and separated from a liquid, is 
called a Precipitate. 

Thus, the common solution of camphor is formed by dissolving the camphor 
gum in alcohol. If water be added to this solution, the alcohol at once mixes 
with the water, and abandons the camphor, which immediately resumes its 
solid form, and falls to the bottom of the vessel — it is precipitated. 

The precipitation of a solid from its solution may also be effected by several 
other methods : — 

Especially may this be accomplished by changing the character of the sub- 
stance held in solution, by bringing in contact with it another body with which 
it is able to unite chemically, and form an insoluble compound. Thus, lime 
is somewhat soluble in water, but if we bring carbonic acid gas in contact 
with it while in solution, the two substances unite together by the action 
of the chemical force of affinity, and overcome the adhesion which the water 
previously had for the lime. The compound of carbonic acid and lime thus 
produced, being solid and insoluble, is immediately precipitated. 

The above case illustrates a general law in chemistry, which may be stated 
as follows : — 

Two substances which, when united, form an insoluble 
compound, generally combine and produce the same com- 
pound when they meet in solution. 

This law is practically taken advantage of in chemical operations for sepa- 
rating the different constituents of a compound from each other, or for detect- 
ing the presence of a body when in solution with other substances. Thus, if 
it is desirable to know whether a perfectly clear spring-water contains lime, 
carbonic acid gas is introduced into it. This uniting immediately with the 
lime, forms an insoluble compound, which is precipitated. On the other hand, 
by reversing the process and introducing a solution of lime, we may be able 
to detect the presence of carbonic acid under the same circumstances. 

The depression of the temperature cf a solution will sometimes cause the 
cohesion of the particles of the solid dissolved to acquiro an ascendancy over 
the force of adhesion. Thus, alum dissolved in hot water will resume in part 

Questions. — What is a precipitate? Give an illustration. How may precipitation be 
effected by changing the character of a substance ? What general law governs the precipi- 
tation of substances from their solutions ? How is this law practically applied io chemical 
operations ? How may precipitation be effected through a depression of the temperature 
of a solution ? 



ADHESION AND CAPILLARY ATTRACTION. 43 

its solid form as the solution is cooled ; and when brandy is exposed to in- 
tense cold, many degrees below that necessary to freeze water, the spirit- 
uous portion retains its liquid form, and separates from the aqueous part, 
which solidifies as ice. 

A remarkable illustration of this action is to be found in the fact that 
ice formed by the freezing of sea-water is, under all ordinary circumstances, 
fresh, and entirely destitute of salt. The great ice-fields which cover the 
ocean in the Arctic and Antarctic regions, are always composed of fresh- water 
ice. Indeed, water in the act of freezing separates completely from every 
thing which it previously held in solution. Even the air contained in water 
is expelled in the act of freezing, and becoming entangled in the thickening 
fluid, gives rise to the minute bubbles generally observed in blocks of ice. 
For a like reason, the ice formed by the congelation of a solution of indigo 
is colorless. 

Elevation of temperature will also effect the separation of bodies in solution. 

When, for instance, a solution of common salt in water is exposed to the 
action of heat, the repulsive power of this agent overcomes not only the 
cohesion of the water, but also its adhesion to the salt; the water assumes 
the aeriform state, and passes off as steam, while the salt, deprived of its 
solvent, resumes the solid state. 

57. Solution and Chemical Combination.— A clear dis- 
tinction exists between a solution and a chemical combi- 
nation, which latter, in ordinary language, is often termed 
a solution. 

A simple solution is occasioned by the action of the 
force of adhesion exerted between the particles of the solid 
and the liquid with which it is brought in contact. In all 
cases of simple solution, the properties of both the solid 
and the liquid are retained. 

Thus sugar, whether in a mass in the hand, or dissolved in water, is the 
same substance ; so also when camphor is dissolved in alcohol, the solution 
partakes of the properties of both, having the smell and taste of both cam- 
phor and spirit. 

When a solid disappears in a liquid through the influ- 
ence of a chemical force exerted between the particles of 
the two substances, the compound is not a true solution, 
but a chemical combination, in v^hich the properties of 
both the solid and liquid are essentially changed. 



Questions. — What are illustrations of this principle ? Why is ice, formed by the freez- 
ing of sea-water, fresh ? What is the occasion of the numerous bubbles observed in 
blocks of ice ? How may precipitation be effected by an elevation of temperature ? State 
and illustrate the difference between solution and chemical combination. 



44 PKINCIPLES OF CHEMISTRY. 

Thus, iron placed in diluted acid disappears in it, but the resulting liquid 
does not contain finely divided iron, but a finely divided compound of iron 
and the acid, which possesses entirely different properties from either of its 
constituents. 

Solution differs also from chemical combination in the varying proportions 
in which it occurs, according to temperature, etc. Thus, a given quantity of 
water at the boiling temperature will dissolve nearly four hundred times moro 
saltpetre than it can at a temperature of 60° ; but in chemical combinations 
the proportions in which bodies unite are fixed and invariable. 

SECTION IV. 

CRYSTALLIZATION. 

58. Crystals. — The particles of most substances, in pass- 
ing from a liquid to a solid condition, have a tendency to 
arrange themselves into regular and symmetrical forms, 
each different substance assuming always a peculiar shape, 
from which it never essentially varies. Such regular geo- 
metrical solids are termed Crystals. 

The number of known crystalline forms is much smaller than the num- 
ber of substances which arc capable of crystallizing, and it therefore follows 
that crystals of various kinds of matter may possess the same form. No 
substance, however, has ever been found to be capable of assuming indiffer- 
ently any form, but most substances are restricted to one form of aystal 
and its modifications. This circumstance enables us, very often, to identify 
a substance, or determine its composition, simply by the shape of its crystals. 
For example, common salt always crystallizes in cubes, alum in octohedrons, 
saltpeter in six-sided prisms, Epsom salts in four-sided prisms, and so on. 

59. Amor'photis Bodies,— A solid whose particles are ar- 
ranged irregularly, and which possesses no definite exter- 
nal form, is said to be amorphous (i. e., without form). 

Every solid body is either amorphous, or crystalline, and many bodies exist 
in both of these conditions. Thus, carbon, in the form of charcoal and lamp- 
black, is amorphous, but in the form of the diamond it is crystalline. 

60. Formation of Crystals.— The usual method of ob- 
taining crystals is to form a strong solution of the sub- 
stance in hot water, as most bodies dissolve more freely in 
water when it is at an elevated temperature than when 

Questions.— What .are crystals? Can a substance in crystallizing assume indifferently 
any form ? What are amorphous bodies? Can a substance be both crystalline and amor- 
phous ? What is the usual method of obtaining crystals ? 



CRYSTALLIZATION. 



45 



cold. As the liquid cools, and the force of cohesion gra- 
dually begins to resume the ascendancy, the separated 
particles of the solid have time to select, as it were, the 
arrangement they will assume, and crystals are formed. 

When a solid is melted, or made to assume a liouid 
form by heating, and allowed to cool quietly, its particles 
also, in most instances, assume a crystalline arrangement. 

Illustrations of this may be seen in the crystalline fracture of zinc and 
antimony. Sulphur, also, crystallizes beautifully on cooling after fusion. 

Water, in freezing, or assuming the solid condition, often shoots into beau- 
tiful crystals, as may be seen by examining the snow-flakes which fall dur- 
ing a period of intense cold, beneath a microscope. These crystals may 
also, under favorable circumstances, be seen with the naked eye, by placing 
the flake upon a dark body cooled below 32° F. Fig. 1G represents some of 
the varied and beautiful forms of snow crystals. 

Fig. 16. 




The same crystals which appear in snow, exist also in ice, but they are 
so blended together that their symmetry is lost in the compact mass. "When 
water freezes, its particles all arrange themselves in ranks and lines which 
cross each other at angles of 60 and 120 degrees. This may be seen by 
examining the surface of water in a saucer while freezing. 

If we fracture thin ice, by allowing a pole, or weight to fall upon it, the 
fracture will have more, or less of regularity, being general^ in the form of 
a star, with six equidistant radii, or angles of 60°. 

Another beautiful illustration of the crystallization of water in freezing, is 
seen in the frost-work upon windows in winter, caused by the congelation 

Questions. — What peculiarities of crystallization does water present in freezing? Has 
ice a crystalline structure ? What occasions the symmetrical arrangement of "frost-work 
upon windows, etc., in winter? 



46 PRINCIPLES OF CHEMISTRY. 

of the vapor of the room when it comes in contact with the colcl surface cf 
the glass. All these frost- work figures are limited by the laws of crystalli- 
. ., and the linos which bound them, form among themselves no angles 
but those of 30°, 00°, and 120°. 

When a substance has been converted, through the ac- 
tion of heat, into a vapor or gas, and then by cooling is 

caused to change back again at once into the solid state, 
its particles arrange themselves so as to form crystals. 

Thus, camphor, or sulphur, if heated in a glass tube, will, be first con- 
verted into vapor, and then deposited in a ring of crystals higher up. at the 
first point where the temperature is sufficiently low. 

In general, it is important to the process of crystalliza- 
tion that the liquid from which the solid body is separating 
should not be shaken or disturbed, but when the forces 
of cohesion and adhesion aro nearly balanced, as in a sat- 
urated solution, it seems necessary that some slight mo- 
tion should be given to the liquid in order to initiate the 
process, which does not commence at all in a state cf 
absolute rest. 

Thus, a saturated hot solution of Glauber's salt, if allowed to cool in per- 
fect stillness, will remain liquid as long as the stillness is preserved, at 
the slightest movement or tremor — even a wave of the hand through the 
air in its vicinity — will instantly transform the solution into a solid mass, 
some of the water entering into the composition of the crystals, and some 
being retained by interstices in their structure. In the same manner, water 
may be cooled eight, or ten degrees below the freezing point and yet remain 
liquid ; but the slightest disturbance, even a vibration of the vessel, will 
cause it to freeze (crystallize) instantaneously. 

The more slowly a liquefied body is brought back to a 
solid state, and the more the liquid is kept at rest after 
the process of crystallization has commenced, the smaller 
will be the number and the larger the size of the crystals 
produced ; but when the solution is caused to solidify very 
quickly, the crystals are numerous, but small and imper- 
fect. 

In the fir;: case the particles of the solidifying hour have time I 
selves regularly upon each other; but in the latter instance the soiidifi- 



Qvtstions. — Under what other circumstances may crys: :.'.'. : .z:.:l m ::.'<:■ place : What 
are important requisites in the process of crystallization? What facts illustrate these 
ditions ? Under what circumstances -sriil crystals be perfect, and when imperfect ? 



CRYSTALLIZATION. 47 

cat-'on takes place so rapidly that the particles attach themselves irregularly, 
and interlace with each other in every direction. In this consists the differ- 
ence between "sugar," or "rock candy" and loaf, or granulated sugar; be- 
tween the fine grained statuary marble and crystallized " spar." 

Crystals have always a tendency to fasten upon any 
foreign substance that occupies a prominent position in 
the liquid which affords them, a circumstance which is 
applied to many useful purposes in the arts. 

Illustrations of this are seen in the formation of the somewhat familiar or- 
nament known as the " alum basket," and in the strings which are stretched 
across the vessels in which pure solutions of sugar crystallize in the manu- 
f icture of " rock candy." "When only two or three very minute crystals can bo 
deposited, it is usual to place a piece of thread or some other suitable sub- 
stance in the liquor ; and upon this support the crystals, if anywhere, will be 
found. In this way the chemist is enabled to draw together and collect 
readily the smallest quantities that can be thrown down from a solution. 

Nothing can be more beautiful than to watch the progress of crystallization 
as it takes place when we suspend a series, or network of threads in a hot 
saturated solution of alum, and then allow the liquor to cool slowly. Tho 
minute invisible atoms are gradually drawn together toward the foundation 
thus afforded, and presently little glittering specks may be discerned entan- 
gled among the fibers, or studding the network of the threads. If the pro- 
cess be well managed, these specks increase steadily in size, by the regular 
addition of fresh atoms to every part ; but if the temperature be not attended 
to, or the solution be improperly disturbed, they increase chiefly in numbers, 
and the larger crystals are apt to be disfigured by adhering to small ones.* 

61. Purification by Crystallization. — A substance in 
crystallizing has a tendency to purify, or separate itself 
from any foreign substances which may have been mingled 
with it. Crystalline form is, therefore, to some extent, a 



* " The beautiful crystalline masses that are sometimes seen in druggists' windows, 
can not be produced without the greatest care and attention, each crystal being separated 
from the liquor when it has attained a sufficient size, and being placed alone in a shallow 
pan, perfectly glazed, at a temperature carefully regulated, and under a solution of a 
specified strength. It is then turned over from day to day, as otherwise the face in con- 
tact with the pan would be prevented from increasing, and a deformed crystal would re- 
sult. It is also carefully supplied with fresh solution from time to time : because, if that 
around it were exhausted, its most prominent angles would be re-dissolved. By neglect- 
ing these precautions, deformed or monstrous crystals are obtained, and are exhibited, 
perhaps, as often as the perfect ones. Crystalline masses of the blue sulphate of copper, 
the red chromate of potash, of alum, and some other chemical compounds, may be pro- 
duced of almost any magnitude that is desired." 

Questions — How does interrupted crystallization affect the physical character of a 
body? What curious tendency do crystals exhibit in separating from a solution? What 
practical application of this is made in the arts ? 



48 PRINCIPLES OF CHEMISTRY. 

guaranty of purify, or at least of the absence of adultera- 
tion ; and hence, in medicine, and in the arts, many sub- 
stances are subjected to tedious and expensive processes for 
no other purpose than to cause them to assume this form. 

Sea-water, in addition to salt, contains a variety of other substances, but 
by the process of evaporating the salt water and crystallizing the salt, most 
of these impurities are separated. A single crystallization gives the salt suf- 
ficiently pure for commercial purposes, but to render it perfectly pure, it is 
necessary to re-dissolve the first crystals in pure water and repeat the pro- 
cess of crystallization several times. 

This principle may be demonstrated by a simple experiment. If we dis- 
solve a small quantity of common salt and saltpetre in warm water, and al- 
low the solution to evaporate slowly, the two substances, which are intimately 
united in the solution, will separate completely from each other in crystal 
lizing — the saltpetre assuming the fcrm of long needles or prisms, and the 
common salt the form of cubes. It is in this way that saltpeter is purified 
preparatory to being used in the manufacture of gunpowder. 

If two bodies, however, which crystallize in the same 
form, be mingled in solution, they can not be separated 
from each other by crystallization. 

The difference in the crystallizing properties of silver and lead has been 
taken advantage of in a recent invention for separating a small quantity of 
silver which exists in almost all the ores of lead. The two metals are melted 
and allowed to cool slowly ; the silver, forming into crystals more easily than 
the lead, solidifies first, and the lead remaining is poured off. 

62. Change in Bulk. — Many substances in crystallizing, 
or in passing from a liquid to a solid state, experience a 
change in bulk. 

Water, at the moment of congelation, increases in bulk, and expands with 
an almost irresistible force. As an illustration, the following experiment 
may be quoted : — Cast-iron bomb-shells, thirteen inches in diameter and two 
inches thick, were filled with water, and their apertures or fuse-holes firmly 
plugged with iron bolts. Thus prepared, they were exposed to the sevcro 
cold of a Canadian winter, at a temperature of about 19° below zero. At 
the moment the water froze, the iron plugs were violently thrust out, and the. 
ice protruded, and in some instances the shells burst asunder, thus demon- 
strating the enormous interior pressure to which they were subjected by 
water assuming a solid state. 



Questions. — Can two substances in solution bo separated from eacli other by tbe act 
of crystallization ? What are practical illustrations of this principle ? Under what circum- 
stances will crystallization fail to effect separation ? What physical change frequently 
accompanies crystallization ? Illustrate this action in the case of water. 



CRYSTALLIZATION. 49 

One thousand parts of water at 32° become dilated by- 
freezing to 1068 parts. 

Iron, in passing from a melted to a solid state, expands in the. same manner 
as water, a fact which renders this metal most suitable for castings. 

Other substances, however, present equally remarkable instances of con- 
traction in passing from a liquid to a solid state, of which gold and lead are 
illustrations ; hence it is impossible to obtain with either of these metals a 
fine casting from a mould. 

63. Mother Liquor, — When a substance separates itself 
in part from a liquid by crystallization, the solution re- 
maining behind is termed the Mother Liquor. 

64. Water of Crystallization, — Some substances are not 
capable of assuming a crystalline form until they have 
chemically combined with a certain definite amount of 
water, termed the water of crystallization. This 
water is not essential to the chemical composition of the 
substance, but merely to its existence in the form of 
crystals. 

Thus, a crystal of alum contains nearly one half its weight of water chemi- 
cally combined with it. Without this water, alum could not assume the crys- 
talline form, although it would retain all its chemical properties unchanged. 
The existence of the water of crystallization in alum may be experimentally 
shown by placing a small crystal of this substance upon a hot surface, when 
it will be observed to foam and melt, and finally settle down into a white 
porous mass. The foaming is occasioned by the evaporation of the water of 
crystallization. 

65. Ef-flo-rcs'cencc. — Some substances containing water 
of crystallization, part with it on exposure to the atmos- 
phere, and crumble down to a fine powder. This action 
is termed Efflorescence. 

If we place half an ounce of crystalline Glauber's salts in a warm place, it 
■will soon lose its transparency, and finally crumble into a white powder, 
weighing hardly a quarter of an ounce. This loss of weight is entirely owing 
to the evaporation of the chemically combined water which imparted to the 
salt its transparency and crystalline form. Common salt, and saltpetre, on 
the contraiy, if treated in a similar way, undergo no change in either appear- 
ance, or weight, because they contain no water of crystallization. 

66. Del-i-qucs'cence. — When a crystalline substance, 



Questions. — To what extent will water expand in freezing ? Why is iron eminently 
suitable for fine castings, and gold and lead unsuitable? What is a mother liquor? 
What is water of crystallization ? What is efflorescence? What is deliquescence ? 

3 



50 PRINCIPLES OF CHEMISTRY. 

on exposure to air, absorbs water, and becomes converted 
thereby into a liquid, or semi-liquid mass, it is said to 
deliquesce, and the phenomenon is termed Deliquescence. 
67. De-crep-i-la'tion. — Some substances, when crystal- 
lized rapidly from a solution, frequently inclose mechan- 
ically within their texture small quantities of the mother 
liquor, the expansion of which, when heated, bursts the 
crystals with a sort of crackling explosion. This pheno- 
menon is known by the name of Decrepitation. 

This result may be exhibited by throwing a small quantity of common 
salt, which has been crystallized rapidly, upon a heated surface. If the salt, 
however, has been crystallized by slow evaporation, it will not decrepitate. 

G8. Native Crystals . — The mineral kingdom presents us with tho 
most splendid examples of crystallized bodies, many of which the chemist is 
able to artificially reproduce in his laboratory. Within the last few years, 
M. Ebelman, an eminent French chemist, has succeeded in producing some 
of the most valuable gems — as, for example, the emerald and the ruby — by 
mixing together in proper proportions the elementary substances which enter 
into their composition, and then exposing the compound to the long-continued 
and intense heat of a furnace used for baking porcelain. 

Some native crystals, however, seem to be beyond the power of art to 
imitate. Of these, the diamond is perhaps the most remarkable. This body 
consists of pure carbon (the same substance with which we are familiar as 
charcoal and as black-lead), but which can not be either fused or dissolved, 
and consequently can not be crystallized by any means at present known. 
Such means have been eagerly sought for, however, since the discovery of 
the composition of the diamond, and there seems no reason why they should 
not at some period be discovered. 

The most perfect crystals of gems are met with in nature of only a moder- 
ate size. The larger ones are less clear, and wanting in transparency and 
luster. The emerald, sufficiently pure for jewelr}*-, does not often exceed an 
inch in length, and seldom so much as this. Transparent sapphires above an 
inch in length are very rare. Crystals of quartz are sometimes found of very 
large size. One at Milan measures 3£ feet in length, 5 J- in circumference, 
and weighs 870 pounds. 

G9. Formation of Crystals in Solid Bodies. — A very re- 
markable change, a variety of crystallization, sometimes 
takes place in the form and arrangement of the particles 
of solid bodies, without their undergoing any alteration 

Questions. — What is decrepitation ? Where are the most splendid examples of crystal- 
lized bodies to be met with ? Are any native crystals capable of being reproduced by 
art ? What crystallized body can not be imitated ? What remarkable change sometimes 
takes place in the particles of solid bodies ? 



CRYSTALLIZATION. 51 

from the se ] id to the liquid state. This subject is one of 
great importance, and its investigation has furnished a 
partial solution of some phenomena that were once re- 
garded as inexplicable. 

The simplest illustration of this action is to be found in the case of sugar. 
"When this substance is melted and allowed to cool, it forms a perfectly trans- 
parent, hard mass, without the slightest trace of crystalline arrangement ; but 
aiter soma months it loses its transparency, becomes white, crystalline, and 
brittle. Similar changes take place also in many other bodies, but in cases 
of thi3 character the cause which produced the result described is not cer- 
tainly known, and has been ascribed to the action of several forces. 

The following illustrations are of a somewhat different character. If we 
submit a piece of metal, even the toughest, to long-continued hammering, or 
jarring, the atoms, or particles of which it is composed, seem to take on a 
new arrangement, and the metal gradually loses all its tenacity, flexibility, 
malleability, and ductility, and becomes brittle. 

The surface of a fresh fracture, under such circumstances, exhibits a dis- 
tinctly crystalline structure. The tenacity of a metal thus rendered brittle 
may be restored again in great measure by heating and slowly cooling — a 
process known in the arts as ; ' annealing." 

A great number of other instances illustrative of the effect of jarring and 
concussion on the structure of metals, might also be adduced. Coppersmiths, 
who form vessels of brass and copper by the hammer alone, can work on them 
only for a short time before they require annealing ; otherwise they would 
crack and fly into pieces. 

For similar reasons, a cannon can only be fired a certain number of times 
before it will burst, and a cannon which has been long in use, although ap- 
parently sound, is always condemned and broken up. The tone of a bell, 
during the two or three first years of use, uniformly increases in strength, 
owing probably to a change in the arrangement of the particles under the 
hammering action in ringing. 

A more important illustration, and one that more closely affects our inter- 
ests, is the liability of railroad car-axles and wheels to break from the same 
cause. A car-axle, after a long lapse of time and use, is almost certain to 
break. 

The explanation of these changes, especially in the case of iron, is as fol- 
lows : — The particles of cast-iron, as may be seen by the naked eye, are crystals, 
more or less perfect in form, and aggregated together by the force of cohesion. 
In the conversion of cast-iron into wrought-iron, each crystal by heating, ham- 
mering, and rolling, is gradually elongated into a thread, so that wrought-iron 
is an aggregation of fibers (fibrous iron, as it is sometimes called), or a series 
of threads kept together by the force of cohesion. "When now a bar of cold, 

Questions. — Give an illustration. How is the strength of iron and other metals affected 
by hammering, jarring, etc. ? Under what circumstances will cannon hurst, and railway 
axles break ? What explanation has been given of these phenomena ? 



52 PRINCIPLES OF CHEMISTRY. 

wrought, or fibrous iron is made to vibrate by shocks communicated either 
by blows of a hammer, or by the rapping of any part of a machine., or by the 
continued rolling and jarring of a railway car upon the rails, the little fine 
threads, or fibers snap one by one, and the particles return to their original 
crystalline, or granular state, and by this change the entire mass is rendered 
brittle. 

TO. Primary Forms of Crystals. — The apparently innu- 
merable variety of figures which various substances as- 
sume in crystallizing, may all be referred to a few regular 
and fundamental forms. 

Each substance has a characteristic form of crystal, 
which is termed its Primary Form. 

Variations of this original form, which may take place 
to any extent so long as a correspondence of angles is 
preserved, are termed Secondary Forms. 

The number of primary or fundamental forms to which 
all other crystalline solids may be referred is six — the 
cube, the square prism, the right rectangular prism, the 
oblique rhombic prism, the oblique rhomboidal prism, and 
the hexagonal prism, or rhombohedron. 

The number of secondary forms is almost innumerable, 
all of which are modifications of the six primary forms. 

Thus, carbonate of lime has been found crystallized in more than six hun- 
dred different secondary forms, but all of them are related to each other, and 
are derivable from one original primary figure, the rhombohedron. 

The study of the geometrical relations of the different crystalline forms to 
each other, belongs to the science of crystallography. The investigations of 
chemistry, however, have contributed much to our knowledge of the laws 
and forces which govern the production of crj-stals, and have furnished some 
explanation of the reason why the several atoms, each invisible on account 
of its minuteness, should arrange themselves in the same manner, and in 
the fitting place, so as to build up a cubical or prismatic crystal, rather than 
an incoherent mass, shapeless and devoid of regularity. 

71. Theory of Crystallization.— It is supposed that the 
atoms, or molecules which make up the body of a crystal, 
are possessed of polarity ; or, in other words, that the two 
opposite -sides of the atoms are like the two opposite poles 

Questions. — What is understood by primary and secondary forms of crystals ? How" 
many primary, or fundamental forms of crystals are recognized ? How many secondary 
forms exist ? Give an illustration of the primary and secondary forms of carbonate of 
lime. Explain the general theory of crystallization. 



CRYSTALLIZATION. 



53 




of a magnet, endowed with opposite forces. 
The action of these forces compels the atom, 
in assuming its place in a crystal, to maintain 
a certain direction as respects the contiguous 
particles (see Fig. 17), in the same way that 
the action of the magnetic forces on a bar of 
steel compels it to maintain a constant direc- 
tion as regards the poles of the earth. 

That the strength of the directive force which influences 
the atoms of matter to assume a symmetrical arrangement 
is not feeble or insignificant, is clearly shown by the enor- 
mous power which crystallizing action exerts. Thus, the expansive force 
of water in freezing, illustrations of which are most familiar, is due entirely to 
a re-arrangement of the particles in crystallizing, and a consequent occupa- 
tion of more space. 

The direction in which the supposed polar forces act, or 
the lines in which, the particles arrange themselves in or- 
der to build up symmetrical solids, are termed the axes 
of the crystal. 

Variations in the number or arrangement of these lines or axes, necessarily 
modify the geometrical form of the crystal, and a consideration of the relation 
which the multitude of crystalline forms sustain to each other 
through their axes, or symmetrical lines of formation, has en- 
abled us to select six primary forms from which all the others 
may be derived. 

Thus, in the first primary form, Fig. 18, which is the cubical, 
or regular form, there are three axes, a a a, all equal and cross- 
ing each other at the center of the crystal at right angles. The same arrange- 
ment of axes holds good in all the secondary forms which are derived from this 
primary form ; and in consequence of this are all regular. In the second 
primary form, the square prism, Fig. 19, there are three axes, all of them at 
right angles to each other, but only two, a a, a a, are of equal length ; the 
third, c c, being either longer or shorter than the others. 

Similar variations exist, also, in the number or inclination of 
the axes of the other primary forms. 

Many facts in science seem to prove that the existence of axes 
ia crystals is not imaginary, but real. Thus, when the arrange- 
ment of a crystalline body is perfectly symmetrical, as it is in all 
crystals belonging to the cubical system, the transmission of light, 
the expansion of heat, the conducting power of heat, and probably 



Fig. 18 


A 


: i cc 


a 




/ 



Fig. 19. 




a 


(£ : | 


a 



Questions. — What are the axes of a crystal ? On what ground do "we recognize 6ix 
primary forms of crystalline solids? What facts ia science seem to prove that the axca 
of crystals have a real existence ? 



54 PRINCIPLES OF CHEMISTRY. 

the power of transmitting sound, electricity, and magnetism, is uniform in 
every direction ; but when the axes of a crystal are unequal ; or, in other 
words, when the action of the molecular force which has given direction to 
the atoms and shaped the crystal, is more powerful in one direction than in 
another, an irregularity in the action of the body on light, and in its expan- 
sive and conductive powers for heat, may be immediately traced. 

I-so-morph'ism. — The term Isomorphism (equal forms) 
is applied to those bodies which can be substituted for one 
another in a chemical compound, without producing any 
change in the crystalline form of that compound. This 
property, is restricted to a comparatively few substances. 

Thus, an oxyd of zinc may replace or be substituted for oxyd of magnesia, 
and an oxyd of iron for an oxyd of copper, in a chemical compound, without 
causing any alteration of crystalline form. As a general rule, however, tho 
change, or substitution of one element of a chemical compound for another 
of different character, occasions a change in the crystalline form of the com- 
pound. 

The consideration of isomorphism is of great importance in chemistry, and 
has added much to our knowledge respecting the nature of the elementary 
atoms of matter. A study of its principles, among other results, has estab- 
lished the existence of such curious relations between certain of the so-called 
elementary substances, as to suggest their derivation from some common and 
unknown form of matter. This subject, under another department, will be 
again referred to. 

72. Di-morph'ism. — The rule that all the crystalline fig- 
ures of any particular substance may be derived from the 
same ultimate form, is subject to several exceptions. Some 
substances are capable of assuming two forms of crystals, 
according to the temperature at which they are produced, 
which are geometrically incompatible with each other ; 
and this difference of crystalline form is associated with 
difference of specific gravity, hardness, color, and other 
properties. Such bodies are termed Dimorphous (two- 
formed). 

The crystals of sulphur found in nature, and the crystals obtained by tho 
slow cooling of a melted mass of sulphur, are entirely different. A beautiful 
instance of this kind is afforded by a compound of iodine and mercury, known 
as the iodide of mercury. The minute particles of this substance are of a 
brilliant scarlet color, but by the application of heat their crystalline arrange- 
ment is changed, and the change is rendered visible to the eye by the sub- 

Qtte6Tioxs.— What is isomorphism? Give an illustration. What is dimorphism? 
What are examples ? 



CRYSTALLIZATION". 55 

stitution of a bright yellow color in place of the scarlet. When the substance 
has become cool, the application of a slight mechanical force, such as a mere 
scratch upon a single point, will change the crystalline arrangement back to 
its original condition, and instantly restore the original color. 

Some few substances are even trimorphous ; that is, they crystallize in 
three different forms. 

73. Clcav'age. — Crystals can not be "broken with equal 
readiness in all directions, but they have a tendency to 
split or divide according to certain determinate lines. 
This property is termed the Cleavage of the crystal. 

Cleavage will often enable us to detect crystalline structure in a body which 
at first appears as a shapeless mass. Thus, in the case of the very common 
mineral known as "Iceland spar," which is a variety of carbonate of lime, if 
we strike gently upon an irregular fragment with a hammer, we shall hud 
that the lines in which fracture occurs are all inclined to each other at angles 
of 105 degrees, and in consequence of this, the detached particles have all 
the form of rhombohedrons. In like manner, mica splits only in leaves, and 
galena, the name applied to the common ore of lead, only in cubes. 

This property of crystals has long been known to jew- 
elers, who have profited by it to alter the form of precious 
stones, in place of resorting to the expensive process of 
cutting. Thus, the diamond will split with a smooth sur- 
face in four directions, and by taking advantage of this, 
a thin layer on a defective side may be smoothly removed 
at a single operation. 

A property analogous to the cleavage of crystals may 
be observed in bodies of a different character. Thus, wood 
splits with greater facility in a direction parallel to its 
fibers than at right angles to them, or, as it is termed, 
" across the grain." 



Questions — What is cleavage ? How will cleavage often enable us to detect crystal- 
line structure in an irregular body ? What practical application has been made of tho 
cleavage of crystals ? 



56 PRINCIPLES OF CHEMISTRY. 

CHAPTER II. 

HEAT. 

74. Iloat and Chemical Action,— Almost every form of 
chemical action is influenced to a greater or less extent by 
the agency of heat. A general knowledge, therefore, of 
the principles and applications of heat is essential to a 
correct understanding of the science of chemistry. 

Heat and Caloric, — Heat is a physical agent, known only 
by its effects upon matter. In ordinary language we use 
the term heat to express the sensation of warmth. Ca- 
loric is the general name given to the physical agent which 
produces the sensation of warmth, and the various effects 
of heat observed in matter. 

75. Two Conditions of Heat.— Heat exists in two very 
different conditions, as Free, or Sensible Heat, and as 
Latent Heat.* 

When the heat retained or lost by a body is attended 
with a sense of increased or diminished warmth, it is called 
sensible heat. 

When the heat retained or lost by a body is not per- 
ceptible to our sense, it is called latent heat.f 

76. Measurement of Heat. — The quantity of heat ob- 
served in different substances is measured, and its effects 
on matter estimated, only by the change in bulk, or ap- 
pearance, which different bodies assume, according as heat 
is added or subtracted. 

77. Distinguishing Characteristic of Heat. — Heat pos- 
sesses a distinguishing characteristic of passing through 
and existing in all kinds of matter at all times. So far as 



'"' Latent, from the Latin word lateo, to be hid. 

t The phenomena of latent heat are further considered under the head of Liquefaction 
j»nd Vaporisation. 

Questions. — What relation exists between heat and chemistry? What is heat? De- 
fine the meaning of the term caloric. In what two conditions does heat exist ? What is 
free, or sensible heat ? What is latent heat ? How is heat measured ? What is the dis- 
tinguishing characteristic of heat ? 



HEAT. 57 

we know, heat is everywhere present, and every body that 
exists contains it without known limits. 

Ice contains heat in large quantities. Sir Humphrey Davy, by friction, ex- 
tracted heat from two pieces of ice, and quickly melted them, in a room cooled 
below the freezing-point, by rubbing them against each other. 

78. Temperature.— The degree of sensible heat a body 
manifests is called its temperature. 

The temperature of a body affords no indication of the real quantity of heat 
which it contains. A pint of boiling water will raise a thermometer to the 
same degree as a gallon of the same water ; yet it is obvious that the larger 
quantity of liquid contains the greater amount of heat. 

Cold is a relative term expressing only the absence of 
heat in a degree ; not its total absence, for heat exists 
always in all bodies. 

A body may feel hot and cold to the same person at the same time, since 
the sensation of heat is produced by a body colder than the hand, provided 
it be less cold than the body touched immediately before ; and the sensation 
of cold is produced under the opposite circumstances, of touching a compara- 
tively warm body, but which is less warm than some other body touched pre- 
viously. Thus, if a person transfer one hand to common spring water imme- 
diately after, touching ice, to that hand the water would feel very warm ; while 
the other hand, transferred from warm water to the spring water, would feel a 
sensation of cold. 

It is a very curious fact, that intense cold produces the same sensation a3 
intense heat. Frozen mercury will blister the part to which it is applied in 
the same manner as red hot iron ; and the physiological action of a freezing 
mixture resembles that of boiling water. Sensations of heat and cold are, 
therefore, merely degrees of temperature, contrasted by name in reference to 
the peculiar temperature of the individual speaking of them. 

79. Diffusion of Heat.— The tendency of heat is to dif- 
fuse, or spread itself among all neighboring substances, 
until all have acquired the same, or a uniform temperature. 

A piece of iron thrust into burning coals becomes hot among them, because 
the heat passes from the coals into the iron, until the metal has acquired an 
equal temperature. 

80. Heat Imponderable. — Heat is imponderable, or does 
not possess any perceptible weight. 

If we balance a quantity of ice in a delicate scale, and then leave it to 



Questions. — What is temperature ? Does the temperature of a body indicate the actual 
quantity of heat it contains ? "What is cold ? May a body feel hot and cold at the same 
time ? What are sensations of heat and cold ? In what manner does heat diffuse itself ? 
Does heat possess weight ? 

3* 



58 PRINCIPLES OF CUEMPSTRY. 

melt, the equilibrium will not be in the slightest degree disturbed. If wo 
substitute for the ice boiling water, or red hot iron, and leave this to cool, 
there will be no difference in the result. Count Eumford, having suspended 
a bottle containing water, and another containing alcohol, to the arms of a 
balance, and adjusted them so as to be exactly in equilibrium, found that the 
balance remained undisturbed when the water was completely frozen, though 
the heat the water had lost must have been more than sufficient to have made 
an equal weight of gold red hot. 

81. Theory of Heat. — The nature, or cause of heat is not 
clearly understood. Two explanations, or theories, have 
been proposed to account for the various phenomena of 
heat, which are known as the mechanical and vibratory 
theories. 

Mechanical Theory,— The mechanical theory supposes 
heat to be an extremely subtile fluid, or ethereal kind of 
matter pervading all space, and entering into combination 
in various proportions and quantities, with all bodies, and 
producing by this combination all the various effects no- 
ticed. 

V ibratory T h e o r y . — Th e vibratory theory, on the con- 
trary, supposes heat to be merely the effect of a species 
of motion, like a vibration or undulation, produced either 
in the constituent particles of bodies, or in a subtile, im- 
ponderable fluid which pervades them. 

"When oho end of a bar of iron is thrust into the fire and heated, the other 
end soon becomes hot also. According to the mechanical theory, a subtilo 
fluid coming out of the fire enters into the iron, and passes from particle to 
particle until it has spread through the whole. When the hand is applied to 
the bar it passes into it also, and occasions the sensation of warmth. Ac- 
cording to the vibratory theory, the heat of the fire communicates to the par- 
ticles of the iron themselves, or to a subtile fluid pervading them, certain vi- 
bratory motions, which motions are gradually transmitted in every direction, 
and produce the sensation of heat, in the same way that the undulations or 
vibrations of air, produce the sensation of sound. 

The fact that vibrations do occur in masses of metal and other substances 
during the passage of heat through them, can be demonstrated by experi- 
ment. Thus, if an irregularly curved bar of hot brass be laid upon a sup- 
port of cold lead, the bar will be thrown into a vibratory state, accompanied 



Questions. — What two theories have heen proposed to account for the origin of heat ? 
What is the mechanical theory? What is the vihratory theory? Illustrate the sup- 
posed production of heat in accordance with the Uvo theories. 



HEAT. 59 

by a somewhat musical sound and a rocking motion ; and this action con- 
tinues so long as an inequality of temperature exists between the two metals. 

There seems to be but little doubt at the present time among scientific men, 
that the theory which ascribes the phenomena of heat to a series of vibra- 
tions, or undulations, either in matter, or a fluid pervading it, is substantially 
correct.. At the same time it is not wholly satisfactory, and neither theory 
will perfectly explain all the facts in relation to heat with which we are ac- 
quainted. For the purpose of describing and explaining the phenomena and 
effects of heat, it is convenient, in many cases, to retain the idea that heat is 
a substance. 

The fact that nature nowhere presents us, neither has art ever succeeded 
in showing us, heat alone in a separate state, is a strong ground for believing 
that heat has no separate material existence. Heat, moreover, can be pro- 
duced without limit by friction, and intense heat is, also . produced by the ex- 
plosion of gunpowder. On the contrary, as arguments in favor of the mate- 
rial existence of heat, we have the fact, that heat becomes instantly sensible 
on the condensation of any material mass, as if it were squeezed out of it : as 
when, on reducing the bulk of a piece of iron by hammering, we render it 
red hot (the greatest amount of heat being emitted with the blows that most 
change its bulk). 

Finally, tne laws of the spreading of heat do not resemble those of the 
spreading of sound, or of any other motion known to us. 

82. Relations of Light and Heat. — The relation between heat 
and light is a very intimate one. Heat exists without light, but all the ordi- 
nary sources of light arc also sources of heat ; and by whatever artificial means 
natural light is condensed, so as to increase its splendor, the heat which it 
produces is also, at the same time, rendered more intense. 

Incandescence. — When a body, naturally incapable of 
emitting light, is heated to a sufficient extent to become 
luminous, it is said to be incandescent, or ignited. 

Flame. — Flame is an ignited gas issuing from a burn- 
ing body. Fire is the appearance of heat and light in 
conjunction, produced by the combustion of inflammable 
substances. 

The ancient philosophers used the term fire as a characteristic of the nature 
of heat, and regarded it as one of the four elements of nature ; air, earth, and 
water being the other three. 



Questions. — Which theory is generally received ? What relations exist between light 
and heat ? Define incandescence. What is flame? What is fire ? 



60 PRINCIPLES OF CHEMISTRY. 

SECTION I. 

SOURCES OF HEAT. 

83. Sources of Heat.— The principal sources of heat of 
which practical advantage may be taken, are the sun, me- 
chanical action, chemical action, and electricity. 

84. The Sun a Source of Heat.— The greatest natural 
source of heat is the sun, as it is also the greatest natural 
source of "light. 

Although the quantity of heat sent forth from the sun is immense, its 
rays, falling naturally, are never hot enough, even in the torrid zone, to 
Fig. 20. kindle combustible substances. By means, however, 

of a burning-glass, the heat of the sun's rays can be 
concentrated, or bent toward one point, called a focus, 
in sufficient quantity to set fire to substances submitted 
to their action. 

Fig. 20 represents the manner in which a burning- 
**_ glass concentrates or bends down the t&js of heat 
until they meet in a focus. 

The greatest natural temperature ever authentically re- 
corded was at Bagdad, in 1819, when the thermometer 
(Fahrenheit's) rose to 120° in the shade. On the west 
coast of Africa the thermometer has been observed as 
high as 108° F. in the shade. Burckhardt in Egypt, and 
Humboldt in South America, observed it at 117° F. in 
the shade. 

About 70° below the zero of Fahrenheit's thermometer 
is the lowest atmospheric temperature ever experienced 
by the Arctic navigators. 

The greatest artificial cold ever measured was 220° F. 
below zero. 

This temperature was obtained some years since by M. batterer, a German 
chemist. Professor Faraday has also produced a cold of 166° F. below 
zero. Neither of these experimenters succeeded in freezing pure alcohol or 
ether. 

The estimated temperature of the space above the earth's atmosphere has 
been estimated at 58° below zero, Fahrenheit's thermometer. 

Questions. — What are the principal sources of heat? What is the greatest source of 
heat ? What is the greatest natural temperature ever observed ? What is the lowest 
natural temperature observed ? What Is the greatest artificial cold ever measured ? 



SOURCES OF HEAT. 61 

85. Mechanical Action, considered as a source of heat, 
includes friction and compression, or percussion. 

Friction.— The supply of heat which can be derived 
from friction is apparently unlimited. 

Savago nations kindle a fire by the friction of two pieces of dry wood ; 
the axles of wheels revolving rapidly frequently become ignited ; and in the 
boring and turning of metal the chisels often become intensely hot. In al) 
these cases the friction of the surfaces of wood or of metal in contact dis' 
turbs the latent heat of these substances, and renders it sensible. 

The following interesting experiment was made by Count Rumford, to ih 
lustrate the effect of friction in producing heat : — A borer was made to re- 
volve in a cylinder of brass, partially bored, thirty-two times in a minute. 
The cylinder was inclosed in a box containing 18 pounds of water, the tern- 
pcrature of which was at first 60°, but rose in an hour to 101°; and in 
two hours and a half the water boiled. The heat thus obtained was calcu- 
lated to be somewhat greater than that given out during the same period by 
the burning of nine wax candles, each f ths of an inch in diameter. 

Recent experiments made by Mr. Joule of England, appear to show that 
the actual quantity of heat developed by friction is dependent simply upon 
the amount of force expended, without regard to the nature of the substances 
rubbed together. Ho found, as the result of a great number of experiments, 
that when water was agitated by means of a horizontal brass wheel, wh'.ch 
was made to revolve, as the wheels of a clock are, by the descent of a weight, 
that the temperature of the water was increased by friction against the 
metal ; and that in this way, one pound of water could be raised in tempera- 
ture one degree by an expenditure of an amount of force sufficient to raise 
772 pounds weight to the height of one foot. When cast-iron was rubbed 
against iron, the force required to produce heat by friction sufficient to ele- 
vate the temperature of a pound of water one degree, was found to be equiva- 
lent to 775 pounds, and when iron was rubbed against mercury, to 774 pounds. 

It thus appears from these experiments, that force expended in producing 
friction is converted into heat, and that when a pound of water is elevated in 
temperature one degree, some force equivalent to the raising of a weight of 
about 772 pounds to the height of one foot is always exerted.* 



* This discovery, that heat and mechanical power are mutually convertible, and thafc 
the relation between them is definite, 772 foot-pounds of motive power being equivalent to 
a unit of heat — that is, to the amount of heat requisite to raise a pound of water through 
one degree of Fahrenheit — is one of the most interesting of modern science, and has led 
to many important deductions. Thus, force is expended by friction in the ebb and flow 
of every tide, and must, therefore, reappear as heat. According to the computations of 
Besscl, the astronomer, 25,000 miles of water flow in every six hours from one quarter of 

Questions. — What does mechanical action, considered as a source of heat, include ? 
What is said of the development of heat by friction ? What experiments were made by 
Count Rumford ? What has recently been determined respecting the production of heat 
by friction ? 



62 PRINCIPLES OF CHEMISTRY. 

Compression, — The reduction of matter into a smaller 
compass by an external or mechanical force, is generally 
attended with an evolution of heat. To such an act of 
compression we apply the term condensation. 

Heat may be evolved from air by condensation. This may be shown by 
placing a piece of tinder in a tube, and suddenly compressing the air con- 
tained in it by means of a piston. The air being thus condensed, parts with 
its latent heat in sufficient quantity to set fire to the tinder at the bottom 
of the .tube. 

Percussion, which is a combination of friction and compression, is a familiar 
method of developing heat. An example of this is seen in the use of the 
common steel and flint, in which the compression occasioned by the violent 
collision of the two substances elicits heat sufficient to set fire to detached 
portions of steel. The striking of iron with a hammer, or the subjection of 
any metal to great and sudden pressure, also develops large quantities of 
heat. 

86. Chemical Action is the principal source resorted to 
for procuring heat artificially. Whenever this occurs 
with a high degree of intensity, heat is produced, accom- 
panied generally by an evolution of light. A common 
fire, of wood or coal, is a familiar illustration of the devel- 
opment of heat and light by chemical action. 

87. Electricity . — The passage of accumulated electricity 
through various substances, or from one medium to an- 
other, generally produces heat. The most intense arti- 
ficial heat with wdiich we are acquainted, is thus produced 
by the agency of the electric, or galvanic current. All 
known substances can be melted or volatilized by it. 

Heat so developed has not been employed for practical or economical pur- 
poses to any great extent ; but for chemical experiments and investigations 
it has been made quite useful. 

88. Other Sources of Heat. — In addition to the above- 
mentioned sources, some heat is derived from the earth 



the earth to another. The store of mechanical force is thus diminished, and the tempe- 
rature of our globe augmented by every tide. We do not, however, possess the data 
which will enable us to calculate the magnitude of these effects. 

Questions. — TIow may heat be produced by condensation ? How by percussion ? What 
is said of chemical action as a source of heat ? What of electricity ? What other sources 
of heat are recognized ? 



COMMUNICATION OF HEAT. 63 

itself, and from the stars and planetary bodies. Heat, 
also, is generated or excited through the organs of a liv- 
ing structure, the result, undoubtedly, of chemical actions 
which are continually going on in the systems of animals 
and plants. Heat thus produced is termed vital, or ani- 
mal heat. 

Experimentation has also proved that the simple act of moistening any- 
dry substance is attended with slight, yet constant disengagement of heat. 
With bodies of mineral origin, when reduced to a fine powder with a view of 
increasing the extent of surface, the rise of temperature does not exceed from 
half a degree to two degrees, Fahrenheit's thermometer ; but with some ani- 
mal and vegetable substances, such as cotton, thread, hair, wool, ivory, and 
well-dried paper, a rise of temperature varying from 2° to even 10° or 14° F. 
has been observed. 

SECTION II. 

COMMUNICATION OF HEAT. 

89. Heat may be communicated in three ways : by 
Conduction, by Convection, and by Kadiation. 

By one or all of these methods, bodies which have been heated, or cooled, 
gradually return to the temperature of surrounding objects. If the body is 
hot. heat passes from it to contiguous bodies ; if cold, it gains heat at the 
expense of those substances which possess a higher temperature. 

The three methods of communicating heat will be considered in the order 
above named. 

90. Conduction. — Heat is said to be communicated by 
conduction when it is transmitted from particle to particle 
of a substance, as from the end of an iron bar placed in 
the fire to that part of the bar most remote from the 
fire. 

Different bodies exhibit a very great degree of differ- 
ence in the facility or power with which they conduct 
heat ; some substances oppose very little resistance to its 
passage, while through others it is transmitted slowly, or 
with great difficulty. 



Questions — How is heat communicated ? In what way is an equilibrium of tempera- 
ture preserved! What is conduction? Is the power of conduction the same in all 
bodies ? 



64 



PRINCIPLES OF CHEMISTRY, 




If we place the end of a short rod of 
glass, and of a rod of iron of equal length, 
in the flame of a lamp, Fig. 21, we shall 
soon be sensible that heat reaches the fin- 
gers more rapidly through the metal than 
through the glass ; and shall have a clear 
proof that these two substances differ, 
greatly in their power of conducting heat. 
The different conducting power of va- 
rious solids may be also strikingly shown 
by taking a series of rods of different materials, but of the same dimensions 
(see Fig. 22), placing a bit of wax, or phosphorus upon one of their extremi- 
ties, and applying to the other extremities an equal degree of heat. The wax 
will melt, or the phosphorus inflame at different 
times, according to the conducting power of the dif- 
ferent solids. 

91. Conductors and Non-conductors, 
■ — All bodies are divided into two classes 
in respect to their conduction of heat, 
viz., into conductors and non-conduc- 
tors. The former are such as allow 
heat to pass freely through them ; the 
latter comprise those which do not give 
an easy passage to it. 
92. Conduction of Solids.*— Of all known substances, the 
metals conduct heat with the greatest facility ; but they 
differ considerably when compared with each other. As a 
general rule, the denser a body is, the better it conducts 
heat. Light, porous substances, more especially those of a 
fibrous naturej are the worst conductors of heat. Of all 
substances, gold is the best conductor of heat, and may 




* The following table exhibits the relative conducting power of different substances, the 
ratio expressing the conducting power of gold being taken at 100 : 



Gold 

Platinum . 
Silver 
Copper . 
Iron 
Zinc 



100-00 
98-10 

07-:-;o 

8>82 
37-41 
36-37 



Tin . 
Lead . 
Marble 
Porcelain . 
Brick earth 



30-38 
17-96 

2-34 
1-22 
1-13 



Questions. — What experiments illustrate this fact ? What are conductors and non- 
conductors? What are good conductors ? What are bad conductors ? What substance 
is the best conductor of heat ? 



COMMUNICATION OF HEAT. 



65 



A thermometer, ira- 
Fia. 23. 



be represented by the number 100 ; then iron will be 
37.4 ; marble 2.3 ; and brick clay 1.1. 

The conducting power of stones is next to that of the 
metals, and crystalline stones are better conductors than 
those which are not crystallized. 

93. Conduction of Liquids, — Liquids conduct heat in a 
very limited degree. 

This may be satisfactorily proved by a number of simple experiments. If 
a small quantity of alcohol be poured on the surface of water and inflamed, it 
will continue to burn for some time. (See Fig. 23.) 
mersed at a small depth below the common surface 
of the spirit and the water, will fail to show any in- 
crease in temperature. 

Another and more simple experiment proves the 
same fact ; as when a blacksmith immerses his red- 
hot iron in a tank of water, the water which sur- 
rounds the iron is made boiling hot, while the water 
not immediately in contact with it remains quite cold. 

If a tube nearly filled with water is held over a 
spirit lamp, as in Fig. 24, in such a manner as to di- 
rect the flame against the upper layers of the water, 
the water at the top of the tube may be kept boiling 
for a considerable time, without occasioning the 
slightest inconvenience to the person who holds it. 

94. Conduction of Gases, — Bodies in 
the gaseous, or aeriform condition are 
conductors of heat than liquids. 
Common air, especially, is one of 
the worst conductors of heat with 
which we are acquainted. 

The non-conducting properties of fibrous 
and porous substances are due almost alto- 
gether to the air contained in their interstices, 
or between their fibers. These are so dis- 
posed as to receive and retain a largo quantity of air without permitting it to 
circulate. 

Woolens, furs, cider-down, etc., are well adapted for clothing in winter, not 




more imperfect 
Fig. 24. 




QxrrsTiONS. — TIow does the conducting power of stones vary ? What is said of tha 
conducting power of liquids? What experiments prove that liquids conduct heat imper- 
fectly ? What is the conducting power of gases ? What of common air ? Why are porous 
and fibrous substances non-conductors? Why are woolens, furs, etc., well adapted for 
clothing? 



66 PRINCIPLES OF CHEMISTRY. 

because they impart any heat to the body, but on account of the large quan- 
tities of air which they contain,, imprisoned between their fibers ; this renders 
them non-conductors, and prevents the escape of heat from the body. 

Blankets and warm woolen goods are always made with a nap or projec- 
tion of fibers upon the outside, in order to take advantage of this principle. 
The nap, or fibers retain air among them, which, from its non-conducting 
properties, serves to increase the warmth of the. material. 

The heat generated in the animal system by vital action has constantly a 
tendency to escape, and be dissipated at the surface of the body, and the rate 
at which it is dissipated depends on the difference between the temperature 
of the surface of the body and the temperature of the surrounding medium. 
By interposing, however, a non-conducting substance between the surface of 
the body and the external atmosphere, we prevent the loss of heat which 
would otherwise take place to a greater or less degree. 

An apartment is rendered much warmer for being furnished with double 
doors and windows, because the air confined between the two surfaces op- 
poses by reason of its non-conducting properties, the communication of 
heat from the interior. 

Snow protects the soil in wunter from the effects of cold in the same way 
that fur and wool protect animals, and clothing man. Snow is made up of an 
infinite number of little crj^stals, which retain among their interstices a largo 
amount of air, and thus contribute to render it a non-conductor of heat. A 
covering of snow also prevents the earth from throwing off its heat by radia- 
tion. The temperature of the earth, therefore, when covered with snow, 
rarely descends much below the freezing-point, even when the air is fifteen 
or twenty degrees colder. Thus roots and fibers of trees and plants are 
protected from a destructive cold. . 

As a non-conducting substance prevents the escape of heat from within a 
body, so it is equally efficacious in preventing the access of heat from without. 
In an atmosphere hotter than our bodies, the effect of clothing would be to 
keep the body cool. Flannel is one of the warmest articles of dress, yet we 
can not preserve ice more effectually in summer than by enveloping it in its 
folds. Firemen exposed to the intense heat of furnaces and steam-boilers, in- 
variably protect themselves with flannel garments. 

Cargoes of ice shipped to the tropics, are generally packed for preservation 
in sawdust ; a casing of sawdust is also one of the most effectual means of 
preventing the escape of heat from the surfaces of steam-boilers and steam- 
pipes. Straw, from its fibrous character, is an excellent non-conductor of 
heat, and is for this reason extensively used by gardeners for' incasing plants 
and trees which arc exposed to the extreme cold of winter. 

Refrigerators, used for the preservation of animal and vegetable substances 
in warm weather, are double-walled boxes, with the spaces between the sides 
filled with powdered charcoal, or some other porous, non-conducting substance. 

Qttestioxs. — Why are blankets made with a nap ? What is the use of clothing? Why 
do double doors and windows render a room warmer ? How does snow protect the soil? 
Why do persons exposed to intense heat wear flannel ? How are refrigerators constructed ? 



COMMUNICATION OF HEAT. 



67 



The so-called " fire-proof" safes are also constructed of double or treble walls 
of iron, with intervening spaces between them filled with gypsum, or " Plas- 
ter of Paris." This lining, which is a most perfect non-conductor, prevents 
the heat from passing from the exterior of the safe to the books and papers 
within. The idea of applying " Plaster of Paris" in this way for the construc- 
tion of safes, originated, in the first instance, from a workman attempting to 
heat water in a tin basin, the bottom and sides of which were thinly coated 
with this substance. The non-conducting properties of the plaster were so 
great as to almost entirely intercept the passage of the heat, and the man, 
to his surprise, found that the water, although directly over the fire, did not 
get hot. 

95. Much of the economy of fuel depends upon a judicious application of 
the principles which regulate the conduction of heat. An instructive illus- 
tration of their importance is exhibited in the man- 
ner in which heat may be economized by an appro- 
priate construction of steam-boilers. Thus, one of 
the most economical forms, which is known as the 
Cornish, or cylinder boiler, consists of two cylinders, 
placed one within the other. (See Fig. 25.) Be- 
tween the two is the space for the water ; the inner 
cylinder contains the furnace, fire-grates, ash-pit, and 
the flue, or chamber through which the products of 
combustion pass off. By this arrangement, the heat 
which would otherwise be conducted away by the 
fire-bars and the masonry of the ash-pit, is taken up by the surrounding 
water, and thus economized. The 



Fig. 25. 




smoke and hot air from the fire also 
pass through the boiler for its whole 
length, which is sometimes as much 
as forty, or even sixty feet, and then 
return along the outside of the boiler 
through a chamber of masonry, be- 
fore they finally escape up the chim- 
ney. 

In the boiler of a locomotive, Fig. 
26, the fire-box is surrounded at the 
top and two sides by a double cas- 
ing containing water, and the hot air 
from the furnace passes through the 
water in the boiler in numerous 
small parallel flues, or tubes, which 
open at one end into the fire-box, 
and at the other into the smoke- 



Fig. 26. 




Questions. — How are safes rendered fire-proof? Illustrate the application of the prin- 
ciples of conduction in the construction of the cylinder hoiler. Also in locomotive hollers. 



68 PRINCIPLES OF CHEMISTRY. 

pipe. By this last arrangement, the heat is, as it were, filtered through the 
water, and is nearly all communicated to it. Loss of heat from the external 
surfaces of locomotive-boilers may be also prevented by casing them with 
wood, or some other non-conducting substance. 

96. Convection. — Liquids and gases, being non-conduc- 
tors, can not well be heated like solids, by the communi- 
cation of heat from particle to particle. Heat, however, 
is diffused through them with great rapidity by a motion 
of their particles, which brings them successively in con- 
tact with the heated surfaces. This process is termed 
Convection. 

Thus, when heat is applied to the bottom of a vessel containing water, the 
particles which constitute the lower layers of liquid expand and become lighter, 
and a double set of currents is immediately established — one of hot particles 
rising toward the surface, and the other of colder particles descending to the 
bottom. The portion of liquid which receives heat from below is thus con- 
tinually diffused through the other parts, and by this motion of the particles 
the heat is communicated. ; 

These currents take place so rapidly, that if a thermom- 
JTiG. 27. eter be pi ace( j a t the bottom and another at the top of a long 

jar (the fire being applied below), the upper one will begin 
to rise almost as soon as the lower one. The circulation de- 
scribed may be rendered visible, by adding to a flask of 
boiling water a small quantity of bran or saw-dust, or a few 
particles of bituminous coal. (See Fig. 27.) 

The process of cooling in a liquid is di- 
rectly the reverse of that of heating. The 
particles at the surface, by contact with the 
air, readily lose their heat, become heavier, 
and sink, while the wanner particles below in 
turn rise to the surface. 

To heat a liquid, therefore, the heat should be applied at the bottom of the 
mass ; to cool it, the cold should be applied at the top, or surface. 

The facility with which a liquid may be heated or cooled, depends in a great 
degree on the mobility of its particles. Water may be made to retain its heat 
for a long time by adding to it a small quantity of starch, the particles of 
which, by their viscidity or tenacity, prevent the free circulation of the heated 
particles of water. For the same reason soup retains its heat lorger than 
water, and all thick liquids, like oil, molasses, tar, etc., require a considerable 
time for cooling. 

Questions.— What is convection ? Illustrate the communication of heat by convection. 
Explain the process of cooling in liquids. What circumstance greatly influences the heat- 
ing and cooling of liquids? 




COMMUNICATION OF HEAT. 69 

97. Heating of Gases and Vapors.— Common air, and all 
gases and vapors, are heated in the same manner as liquids. 
From every heated substance, an upward current of air is 
continually rising. 

It is in accordance with this principle that we are enabled to readily warm 
the air of an apartment by means of a stove, or furnace. The air in immediato 
contact with the hot surface becomes heated and rises, while cooler and 
heavier air rushes in from all sides to supply its place. This,. in turn, becomes 
heated and ascends, and thus a circulation similar to that which occurs in a 
flask of boiling water, is established. 

98. Winds and Ocean Currents. — The processes of circu- 
lation produced by heat in liquids and in gases, which 
have been described, occur upon avast scale iu the atmos- 
phere and in the ocean. 

Aerial currents are most powerful at the equator, the warm air of which rises 
and incessantly flows in the upper regions of the atmosphere toward the 
poles ; while just as constantly, at the earth's surface, currents of cool air, 
constituting the trade winds, flow from the poles to the equator. 

Similar currents are produced by the same cause in the waters of the 
ocean. Their power may be inferred from the influences which in some cases 
they exert upon climate. By them the warm water of the Gulf of Mexico 
is carried to the British Isles, thereby producing a mild, uniform warmth, 
and a rich moisture ; while through similar causes, the floating ice of the 
North Pole is carried to the coast of Newfoundland, and produces, cold.* 

99. Radiation.— When the hand is placed near a hot 
body suspended in the air, a sensation of warmth is per- 
ceived, even for a considerable distance. If the hand be 
held beneath the body, the sensation will be as great as 
upon the sides, although the heat has to shoot down 
through an opposing current of air approaching it. This 
effect does not arise from the heat being conveyed by 



• Further, by the heat of the sun a portion of the water is converted into vapor, which 
rises in the atmosphere, is condensed into clouds, or falls as rain or snow upon the earth ; 
collects in the form of springs, brooks, and rivers ; and finally reaches the sea again, after 
having gnawed the rocks, carried away the light earth, and thus performed its part ia tha 
geologic changes of the earth ; perhaps, beside all this, it has driven our water-mill on 
its way. If the heat of the sun were withdrawn, there would remain only a single mo- 
tion of water (provided it remained a liquid), namely, the tides, which are produced by 
the attraction of the sun and moon. 

Questions. — How are gases and vapors heated? Upon what principle are rooms 
warmed by stoves and furnaces ? What is the occasion of winds and ocean currents ? 
Define radiation. 



70 PKINCIPLES OF CHEMISTRY. 

means of a hot current, since all the heated particles have 
a uniform tendency to rise ; neither can it depend upon 
the conducting power of the air, because aeriform sub- 
stances possess that power in a very low degree, while the 
sensation in the present case is excited almost on the in- 
stant. This method of distributing heat, to distinguish it 
from heat passing by conduction, or convection, is called 
radiation, and heat thus distributed is termed radiant, or 
radiated heat. 

Heat is communicated through space by radiation in 
straight lines, and its intensity diminishes as the square of 
the distance from the center of action increases. 

Thus the heating effect of any hot body is nine times less at threo feet 
than at one ; sixteen times less at four feet ; and twenty-live times less at 
five. 

All bodies radiate heat in some measure, but not all 
equally well ; radiation being generally in proportion to 
the roughness of the radiating surface. All dull and dark 
substances are, for the most part, good radiators of heat ; 
but bright and polished substances are generally bad 
radiators. Color, however, alone, has no effect on the 
radiation of heat. 

A liquid contained in a bright, highly -polished metal pot, will retain its 
heat much longer than in a dull and blackened one. This is not due to the 
polish or brightness of the surface, but to the fact that, by polishing, the sur- 
face is rendered dense and smooth, and such surfaces do not allow the heat to 
escape readily. If we cover the polished metal surface with a thin cotton or 
linen cloth, so as to render the surface less dense, the radiation of heat, and 
consequent cooling, will proceed rapidly. 

Black lead is one of the best known radiators of heat, and on this account 
is generally employed for the blackening of stoves and hot-air flues. As a 
high polish is unfavorable to radiation, stoves should not be too highly polished 
with this substance. 

The great supply of heat to the, earth from the sun is transmitted by tho 
process of radiation. Some idea of the amount of heat thus received by the 
earth may be formed from a calculation of Professor Faraday, which indicated 
that the average amount of heat radiated in a summer's day upon each acre 



Questions. — How is heat communicated by radiation ? What circumstances influence 
radiation? What are good and bad radiators? What amount of heat does the earth re- 
ceive by radiation from the sun ? 



COMMUNICATION OF HEAT. 71 

of land in the latitude of London, is not less than that which would be pro- 
duced by the combustion of 18,000 pounds of coal. 

The radiation of heat goes on at all times, and from all 
surfaces, whether their temperature be the same as, or dif- 
ferent from that of surrounding objects ; therefore the 
temperature of a body falls when it radiates more heat 
than it absorbs ; its temperature is stationary when the 
quantities emitted and received are equal ; and it grows 
warm when the absorption exceeds the radiation. 

If a body, at any temperature, be placed among other bodies, it will affect 
their condition of temperature, or as we express it, it will affect them ther- 
mally ; just as a candle brought into a room illuminates all bodies in its pres- 
ence ; with this difference, however, that if the candle be extinguished, no 
more light is diffused by it ; but no body can be thermally extinguished. All 
bodies, however low be their temperature, contain heat, and therefore radiate 
it. 

If a piece of ice be held before a thermometer, it will cause the mercury in 
its tube to fall, and hence it has been supposed that the ice emitted rays of 
cold. This supposition is erroneous. The ice and the thermometer both 
radiate heat, and each absorbs more or less of what the other radiates toward 
it. But the ice, being at a lower temperature than the thermometer, radiates 
less than the thermometer, and therefore the thermometer absorbs less than 
the ice, and consequently falls. If the thermometer placed in the presence 
of the ice had been at a lower temperature than the ice, it would, for liko 
reasons, have risen. The ice in that case would have warmed the ther- 
mometer. 

100. Disposition of Radiant Heat. — When rays of heat 
radiated from one body fall upon the surface of another 
body, they may be disposed of in three ways : 1. They 
may rebound from its surface, or be reflected ; 2. They 
may be received into its surface, or be absorbed ; 3.' They 
may pass directly through the substance of the body, or 
be transmitted. 

101. Reflection of Heat. — Polished metallic surfaces con- 
stitute the best reflectors of heat ; but all bright and light 
colored surfaces are adapted for this purpose to a greater, 
or less degree. 

"Water requires a longer time to become hot in a bright tin vessel than in a 

Questions. — Does radiation proceed constantly from all bodies ? Why does the mer- 
cury of a thermometer sink when brought near ice ? When radiant heat falls upon the 
surface of a body, how may it be disposed of? What surfaces are good reflectors of heat ? 



72 PRINCIPLES OF CHEMISTRY. 

dark colored one, because the heat is reflected from the bright surface, and 
does not enter the vessel. 

The power of reflection of heat seems to reside almost exclusively in the 
surface. A film of gold leaf, not exceeding l-200,000th of an inch in thick- 
ness, answers the purpose of a reflector nearly as well as a mass of solid gold. 

102. Absorption of Heat.— The power of absorbing heat 
varies with almost every form of matter. Surfaces are 
good absorbers of heat in proportion as they are poor re- 
flectors. The best radiators of heat also are the most pow- 
erful absorbers, and the most imperfect reflectors. 

Dark colors absorb heat from the sun more abundantly than light ones. 
This may be proved by placing a piece of black and a piece of white cloth 
upon the snow exposed to the sun ; in a few hours the black cloth will have 
molted the snow beneath it, while the white cloth will have produced little 
or no effect upon it. 

A piece of brown paper submitted to the action of a burning-glass, ignites 
much more quickly than a piece of white paper. The reason of this is, that 
the white paper reflects the rays of the sun, and though but slightly heated 
appears highly luminous; while the brown paper which absorbs the rays, 
readily becomes heated to ignition. For the same reason a kettle whose bot- 
tom and sides are covered with soot, heats water more readily than a kettle 
whose sides are bright and clean. 

Air absorbs heat very slowly, and does not readily part with it. Air is not 
heated to any extent by the direct rays of the sun. The sun, however, heats 
the surface of the earth, and the air resting upon it is heated by contact with 
it, and ascends, its place being supplied by colder portions, which in turn are 
heated also. 

This reluctance of air to part with its heat occasions some very curious dif- 
ferences between its burning temperature and that of other bodies. Metals, 
which are generally the best conductors, and therefore communicate heat 
most readily, can not be handled with impunity when raised to a temperature 
of more than 120° F. ; water becomes scalding hot at 150° F. ; but air ap- 
plied to the skin occasions no very painful sensation when its heat is far be- 
yond that of boiling water. 

103. Formation of Dew. — Dew is the moisture of the 
air condensed by coming in contact with bodies colder 
than itself. 

As soon as the sun has set in summer, and the earth is -no longer receiving 
new supplies of heat, its surface begins to throw off the heat (which it has 

Questions. — Where does the power of reflecting heat reside in solid bodies ? How- 
does the power of absorbing heat vary in different substances ? What are good absorbers 
of heat? What are the peculiarities of air as respects absorption of heat ? How is the 
atmosphere heated? What curious experiments illustrate the retention of heat by the 
air ? What is dew ? To what is the formation of dew owing ? 



COMMUNICATION OF HEAT. 73 

accumulated during the day) by radiation ; tho air, however, does not radiate 
its heat, and, in consequence, the different objects upon the earth's surface 
are soon cooled down from 1 to 25 degrees below the temperature of the sur- 
rounding atmosphere. The warm vapor of the air, coming in contact with 
these cool bodies, is condensed and precipitated as dew. 

All bodies have not an equal capacitj^ for radiating heat, but somo cool 
much more rapidly and perfectly than others Hence it follows, that with 
the same exposure, some bodies will be densely covered with dew, while 
others will remain perfectly dry. Grass, the leaves of trees, wood, etc., radiate 
heat very freely ; but polished metals, smooth stones, and woolen cloth, part 
with their heat slowly : the former of these substances will therefore be com- 
pletely drenched with dew, whilo the latter, in the same situations, will be 
almost dry. 

The surfaces of rocks and barren lands are so compact and hard, that they 
can neither absorb nor radiate much heat ; and (as their temperature varies 
but slightly) little dew is deposited upon them. Cultivated soils, on the 
contrary (being loose and porous) very freely radiate by night the heat which 
they absorb by day ; in consequence of which they are much cooled down, 
and plentifully condense the vapor of the air into dew. Such a condition 
of things is a remarkable evidence of design on the part of the Creator, since 
every plant and inch of land which needs the moisture of dew is adapted to 
collect it ; but not a single drop is wasted where its refreshing moisture is not 
required. 

Dew is always formed upon the surface of the material 
upon which it is found, and does not fall from the atmos- 
phere. 

104. Frost is frozen dew. When the temperature of 
the body upon which the dew is deposited sinks below 32° 
F., the moisture freezes and assumes a solid form, consti- 
tuting what is called "frost." 

105. Dew-Point. — The temperature at which the con- 
densation of moisture in the atmosphere commences, or 
the degree indicated by the thermometer at which dew 
begins to be deposited, is called the " Dew-Point." 

This point is by no means constant or invariable, since dew is only de- 
posited when the air is saturated with vapor, and the amount of moisture re- 
quired to saturate air of high temperature is much greater than for air of 
low temperature. 

If the saturation be complete, the least diminution of temperature is at- 
tended with tho formation of dew ; but if the air is dry, a body must be 

Questions. — Is dew deposited equally upon all substances? Does dew fall ? What is 
frost ? What is the dew-point ? 

4 



74 PRINCIPLES OF CHEMISTRY. 

several degrees colder before moisture is deposited on its surface ; and indeed 
the drier the atmosphere, the greater will be the difference between the tem- 
perature and its dew-point. 

Dew may be produced at any time by bringing a vessel of cold water into 
a warm room. The sides of the vessel cool the surrounding air to such an 
extent that it can no longer retain all its vapor, or, in other words, the tem- 
perature of the air contiguous to the cold surface is reduced below the dew- 
point ; dew therefore forms upon the vessel. A pitcher of water under such 
circumstances is vulgarly said to " sweat." 

106. Transmission of Heat.— Heat derived from the 
sun, like light emanating from the same source, passes 
through all transparent bodies, without material loss ; 
but heat derived from terrestrial and less intense sources, 
is in great part arrested by many substances, which allow 
light to pass freely. 

Thus, a plate of glass held between one's face and the sun will not protect 
it, but held between the face and a fire, it will intercept a large proportion of 
the heat. 

The power of heat to penetrate a dense transparent 
substance increases in proportion as the temperature of 
the body from which it is radiated increases. 

Rock-salt appears to be the only substance which transmits an equal 
amount of heat from all sources. It has, hence, been called the " glass of 
heat," since it permits heat to pass with the same ease that glass does light. 
Alum, on the contrary, which is nearly transparent, almost entirely intercepts 
the passage of terrestrial heat. Heat, indeed, will pass more readily through 
a black glass, so dark that the sun at noonday is scarcely discernible through 
it, than through a thin plate of clear alum. 

Transparent substances of considerable density, such as glass, alum, water, 
rock-crystal, etc., interfere most with the passage of heat ; while transparent 
substances of little denshy, as air, the various gases, etc., allow heat to pass 
with comparatively little interruption. 

Those substances which transmit heat most freely, are 
termed diatliermanous ; and those which intercept the 
rays of heat more or less completely, athermanous. 

Questions. — State the peculiarities which distinguish the transmission of heat derived 
from different sources? Upon what does the power of heat to penetrate a substance de- 
pend? What substance transmits heat most readily? What least so? What terms 
have been used to indicate the difference in bodies as respects the transmission of heat? 



THE EFFECTS OF HEAT. 75 

SECTION III. 

THE EFFECTS OF HEAT. 

107. Universal Influence of Heat —The form of all 
bodies appears to be materially affected by heat ; by its 
increase solids are converted into liquids, and liquids into 
vapor ; by its diminution vapors are condensed into liquids, 
and these in turn become solids. 

If matter ceased to be influenced by heat, all liquids, vapors, and doubtless 
even gases, would become permanently solid, and all motion on the surface 
of the earth would be arrested. 

108. Specific Heat. — All bodies contain incorporated 
with them more or less of heat ; but equal weights of dis- 
similar substances require unequal quantities of heat to 
elevate them to the same temperature. 

Thus, if we place a pound of water and a pound of mercury over a fire, it 
will be found that the mercury will attain to any given temperature much 
quicker than the water. Or if we perform the converse of this experiment, 
and take two equal quantities of mercury and water, and having heated them 
to the same degree of temperature, allow them to cool freely in the air, it will 
be found that the water will require much more time to cool down to a com- 
mon temperature than the mercury. The water obviously contains more heat 
at the elevated temperature than the mercury, and therefore requires a longer 
time to cool. 

Dissimilar substances require, respectively, different 
quantities of heat to raise their temperature one degree ; 
and the quantity of heat required to raise any substance 
one degree in temperature, as compared with the quantity 
required to raise an equal weight of some other substance, 
selected as a standard of comparison, one degree, is called 
its specific heat. In like manner, the weight which a 
body includes under a given volume, is termed its specific 
weight. Water is adopted as the standard for comparing 
the different quantities of heat which equal weights of 
dissimilar substances contain. 

Questions. — What is said respecting the universal influence of heat? Is the same 
amount of heat contained in all substances ? What experiment proves that water contains 
more heat than mercury? What is specific heat ? What standard is adopted for com- 
paring the heat of different substances ? 



76 PRINCIPLES OF CHEMISTRY. 

109. Capacity for Heat. — A substance is said to have a 
greater, or less capacity for heat, according as a greater, 
or less quantity of heat is required to produce a definite 
change of temperature, or an elevation of temperature of 
one degree. 

In general, the capacity of bodies for heat decreases with their density. 
Thus mercury has a less capacity for heat than water, because its density is 
greater. Air that is rarefied, or thin, has a greater capacity for heat than 
dense air. This circumstance will explain, in part, the reason of the very low 
temperatures which exist at great elevations in the atmosphere. Persons 
ascending high mountains, or in balloons, find that the cold increases with 
the elevation. The reason of this is, that the air in the upper regions of the 
atmosphere, relieved from superincumbent pressure, is expanded and rarefied ; 
its capacity for heat is, therefore, greatly increased, and it absorbs its own 
sensible heat. 

In all quarters of the globe, the temperature of the air at a certain height 
is reduced so low by its rarefaction, that water can not exist in a liquid state. 
This limit, the height of which varies, being the most elevated at the equator, 
and the most depressed at the poles, is called the line of Perpetual Snow.* 

If compressed air be allowed suddenly to expand, by escaping into the at- 
mosphere, the rarefaction produced increases its capacity for heat ; it, there- 
fore, absorbs heat most readily, and occasions a sensation of cold. It is on 
this account that air forcibly expelled from the mouth feels cool. 

On the contrary, if we compress a quantity of air, and render it more dense, 
we diminish its capacity for heat, and it becomes incapable of retaining what 
was before incorporated into its substance. The proof of this may be found 
in the fact, that by the sudden compression of a small quantity of air in a 
suitable vessel we may obtain a sufficient amount of heat to ignite tinder and 
other inflammable substances. 

The capacity for heat increases with the temperature. 
Thus it requires a greater amount of heat to elevate the 
temperature of platinum from 212° to 213°, than from 
32° to 33°. 

A body in a liquid state has a higher specific heat 
than the same substance when it is in the solid form. 



* The line of perpetual snow at the equator occurs at a height of ahout 15,000 feet ; at 
the Straits of Magellan, it occurs at an elevation of only 4,000 feet. 



Questions. — What is understood by capacity for heat? How does the capacity cf 
bodies for heat increase ? Why is the temperature of air at high elevations very much 
reduced ? Why does the compression of air produce heat ? How does the capacity for 
heat vary with the temperature ? 



THE EFFECTS OF HEAT. 77 

This is remarkably shown in the case of water, the specific 
heat of which is double that of ice. 

Of all known substances, water has the greatest capacity for heat. This 
circumstance renders the ocean a great reservoir of heat, and a regulator of 
temperatures upon the surface of the earth. Thus in hot weather, the water 
of the ocean, on account of its great capacity for heat, absorbs and retains 
large quantities from the air ; the air, therefore, accumulates heat but slowly. 
In cold weather, the heat previously absorbed by the ocean is gradually re- 
stored to the air, and a sudden reduction of atmospheric temperature is pre- 
vented. It is, therefore, mainly on this account that sea-coasts and islands 
enjoy a more uniform temperature than the interior of continents. In tho 
summer, the proximity of the sea serves to mitigate the heat ; in the winter, 
to diminish the cold. Inland lakes, in like manner, raise the mean tempera- 
ture. The climate of the shores of Lake Erie is much milder than that of the 
adjacent inland country, and fruit maybe successfully cultivated at Cleveland, 
upon the southern shore, which fails to ripen in districts further south. 

An ocean of mercury would produce very different results, since it is ca- 
pable of absorbing but a small amount of heat, which it readily parts with at 
a slight reduction of temperature. 

110. Cal-o rim'e-try— The art of determining the spe- 
cific heat of various substances is called Calorimetry. 

Several different methods may be employed for this purpose. One method 
consists in inclosing equal weights of different substances, heated to the same 
temperature, in closed cavities in a block of ice, and measuring the respective 
quantities of water which they produce by melting the ice. 

The same result may also be obtained by what is called the method of mix- 
tures. Thus, if we mix 1 pound of mercury at 66° with 1 pound of water 
at 32°, the common temperature will be 33°. Here the mercury loses 33° 
and the water gains 1°; that is to say, the 33° of the mercury only elevates 
the water 1°, therefore the capacity of water for heat is 33 times that of 
mercury ; or, if we call the capacity or specific heat of water 1, then the capacity, 
or specific heat of mercury, as compared with water, will be l-33d, or .303. 

In this way the specific heat of a great number of bodies has been deter- 
mined, and tables constructed in which they are recorded. 

111. Apparent Effects of Heat.— The three most appa- 
rent effects of heat, so far as they relate to the form and 
dimensions of bodies, are Expansion, Liquefaction, and 
Vaporization. 

112. Theory of Expansion. — Heat operates to produce 

Questions. — What substance has the greatest capacity for heat ? How do great bodies 
of water serve to regulate temperature ? What is calorimetry ? How is the specific heat 
of bodies determined? What are the three most apparent effects of heat? How does 
heat produce expansion ? 



78 PRINCIPLES OF CHEMISTRY. 

expansion by introducing a repulsive force among the 
particles of the body it pervades. This repulsive force 
gives to the particles a tendency to separate, or increase 
their distance from one another. Hence the general mass 
of the body is made to occupy a larger space, or expand. 

The expansion occasioned by heat is greatest in those 
bodies which are the least influenced by cohesion. Solids 
expand less for equal elevations of temperature than 
either liquids or gases. 

The expansion of the same body will continue to in- 
crease with the quantity of heat that enters it, so long 
as the form and chemical constitution of the body is pre- 
served. 

113. Expansion of Solids.— Solids appear to expand uni- 
formly from the freezing point of water up to 212°, the 
boiling point of water ; — that is to say, the increase of 
volume which attends each degree of temperature which 
the body receives is equal. When solids are elevated, 
however, to temperatures above 212°, they do not dilate 
uniformly, but expand in an increasing ratio. 

Different solids, however, expand Yery unequally for 
equal additions of temperature. 

Among solids the metals expand the most ; but an iron wire increases only 
p 1-282 in bulk when heated from 32° of the 

thermometer up to 212°. Zinc is the most 
expansible of the metals, and platinum the 
most uniform in its rate of expansion at all 
temperatures. "Wood and marble expand 
but slightly. 

The expansion of solids by heat is clearly 
shown by the following experiment, Fig. 
28. m represents a ring of metal, through 
which, at the ordinary temperature, a small 
iron or copper ball, a, will pass freely, this 
ball being a little less than the diameter of 
the ring. If this bail be now heated by the 

flame of an alcohol lamp, it will expand by heat to such an extent as no 

longer to pass through the ring. 

Questions. — What bodies expand most under the influence of heat ? Is the expansion 
of bodies by heat limited ? What is the law of expansion for solids ? 




THE EFFECTS OF HEAT. 79 

Bodies, in general, expanded under the influence of 
heat, return to their original dimensions in cooling. 

Lead, however, is an exception to this rule. From its extreme softness, 
its particles slide over each other in the act of expansion, and do not return 
to their original position. " A leaden pipe, used for convoying steam, perma- 
nently lengthens some inches in a short time, and the leaden flooring of a 
sink, which often receives hot water, becomes, in the course of use, thrown 
up into ridges and puckers." 

114. Fores of Expansion.— The force with which bodies 
expand and contract under the influence of the increase 
or diminution of heat^ is apparently irresistible, and is re- 
cognized as one of the greatest forces in nature. 

The amount of force with which a solid body will ex- 
pand or contract through the inflaence of heat, is equal 
to that which would be required to compress it by me- 
chanical means through a space equal to its expansion, or 
elongate it through a space equal to its contraction. 

A bar of malleable iron, having a section of a square inch, is stretched 
l-10,000th of its length by a ton weight ; a similar elongation is produced by 
the influence of about sixteen degrees of heat, Fahrenheit. In this climate, a 
variation of 80° F. between the cold of winter and the heat of summer not 
unfrequently takes place. Within these limits, a wrought iron bar ten inches 
long will vary in length 5-1, 000th of an inch; and is capable of exerting a 
strain of fifty tons upon a square inch. 

Experiments made a few years since demonstrated, that 
Bunker Hill monument is caused to vary each day from 
a vertical position, by the heat of the sun expanding un- 
equally the granite of which it is constructed. 

The expansion of solids by heat is made applicable for many useful pur- 
poses in the arts. The tires of wheels, and hoops surrounding water-vats, 
barrels, etc., are made in the first instance somewhat smaller than the frame- 
work they are intended to surround. They are then heated red hot and put 
on in an expanded condition ; on cooling, they contract and bind together the 
several parts with a greater force than could be conveniently applied by any) 
mechanical means. In like manner, in constructing steam-boilers, the rivet3 i 
are fastened while hot, in order that they may, by subsequent contraction, 
bind the plates together more firmly. 

In many operations, however, the force of expansion requires to be care- 

Qttebtiotjs. — Is expansion by heat counteracted by cooling? With what force do bodies 
expand and contract by the increase, or diminution of heat ? Mention some instances of 
expansion in the arts ? In what cases is it necessary to guard against the expansion of 
Bolids ? 



80 



PRIITCIPLES OF CHEMISTRY. 



fully guarded against. This is especially the case when iron is combined in 
any structure with less expansible materials. 

Iron clamps and bars, built into walls of masonry, frequently weaken, or 
destroy, by their expansion and contraction, the structure they were intended 
to support. Iron pipes used lor the conveyance of steam or hot water, should 
not be allowed to abut against a wall, or substance which might be moved, 
or injured by their expansion. 

115. Expansion of Liquids,— Liquids expand through 
the agency of heat more unequally, and to a much greater 
extent than solid?. 

A column of water contained in a cylindrical glass vessel will expand 
l-23d in length on being heated from the freezing to the boiling point, while 
a column of iron, with the same increase of temperature, will expand only 
l-846th. 

A familiar illustration of the expansion of water by heat is seen in the over- 
flow of full vessels before boiling commences. 

Different liquids expand very unequally with an equal increase in tem- 
perature. 

This may be illustrated by partially filling several glass tubes furnished 
with bulbs, with different liquids, as ether, alcohol, water, and sulphuric acid, 
and placing them in a vessel of hot water. Their 
different rates of expansion will cause them to rise 
to different heights in the tubes. (See Fig. 29.) 

Spirits of wine, on being heated from 32° to 
212°, increase in bulk one ninth; the oils expand 
one twelfth, and water gains one twenty-third. A 
person buying oil, molasses, and spirits in winter 
will obtain a greater weight of the same material, 
in the same measure, than in summer. Spirits, in 
the height of summer, will measure five per cent, 
more than in the depth of winter, or twenty gal- 
lons bought in January will, under ordinary circumstances, become twenty- 
one in July. 

116. Unequal Expansion of Water.— Water, as it de- 
creases in temperature toward the freezing point, exhibits 
phenomena which are wholly at variance with the general 
law that bodies expand by heat and contract by cold, or 
by a withdrawal of heat. 

As the temperature cf water is lowered, it continues to contract until it 
arrives at a temperature of 39° F., when all further contraction ceases. The 
volume or bulk is observed to remain stationary for a time, but en lowering 



PIG. 29. 




QuT-stions. — WTiat is said of tho expansion of liquids ? What peculiarities of expansion 
does water exhibit ? 



THE EFFECTS OF HEAT. 81 

the temperature still more, instead of contraction, expansion is produced, and 
this expansion continues at an increasing rate until the water is congealed. 

Water attains its greatest density, or the greatest 
quantity is contained in a given bulk, at a temperature of 
39° F. 

As the temperature of water continues to decrease below 39°, the point of 
its greatest density, its particles, from their expansion, necessarily occupy a 
larger space than those which possess a temperature somewhat more elevated. 
The coldest water, therefore, being lighter, rises and floats upon the surface 
of the warmer water. On the approach of winter this phenomenon actually 
takes place in our lakes, ponds, and rivers. "When the surface water becomes 
sufficiently chilled to assume the form of ice, it becomes still lighter, and con- 
tinues to float. By this arrangement, water and ice being almost perfect 
non-conductors of heat, the great mass of the water is protected from the 
influence of cold, and prevented from becoming chilled throughout. 

A few other liquids beside water expand with a reduction of temperature. 
Fused iron, antimony, zinc, and bismuth, are examples of such expansion. 
Mercury is a remarkable instance of the reverse, for when it freezes, it suffers 
a very great contraction. 

The ordinary temperature at which water freezes is 32°, Fahrenheit's ther- 
mometer. This rule applies only to fresh water ; salt water never freezes 
until the surface is cooled down to 27°, or five degrees lower than the freezing 
point of fresh water. 

117. Expansion of Gases,— G-ases are more expansible 
by heat than either solids, or liquids. All gases and all 
vapors, except at the point of condensation, are expanded 
equally by the application of equal additions of heat. The 
rate of expansion is equal to the l-490th of the bulk which 
a gas possesses at 32° F. for every degree of heat which, it 
receives above that point, and for every degree of heat 
withdrawn from them a contraction to an equal amount 
takes place. 

Thus 490 cubic inches of air at 32° F. becomes 491 cubic inches at 33° F. ; 
at 34° F., 492 cubic inches ; at 35°, 493, and so on — the addition of every 
degree of heat increasing its bulk one cubic inch. In a like manner, by the 
withdrawal of heat, 490 cubic inches of air would occupy an inch less space 
at 31° than at 32° ; two inches less at 30°, and so on. 

By means of this law we can easily calculate the amount of space which a 

Qukbtions. — At what temperature does -water possess the greatest density? What 
beneficial results attend the expansion of water in freezing? Do any other liquids ex- 
pand in cooling beside water? At what temperature does water freeze? In what man- 
ner do gases expand ? What law governs the expansion of gases ? How can wo calculate 
the amount of space a gas occupies at a given temperature ? 

4* 



82 PRINCIPLES OF CHEMISTRY. 

given volume of gas will occupy, when heated up to any particular tempera- 
ture ; or the contraction which will take place in its volume through a reduc- 
tion of temperature. A given volume of air possessing the temperature of 
freezing water, will occupy double the space when heated 400 degrees; and 
three times the space when heated 080 degrees. 

118. Theory of Heat Measurement. — As the magnitude 
of every body changes with the heat to which it is exposed, 
and as the same body, when subjected to calorific influ- 
ences under the same circumstances has always the same 
magnitude, the expansions and contractions which are the 
constant effects of heat, may be taken as the measure of 
the cause which produced them. 

The instruments for measuring heat are Thermometers 
and Pyrometers. The former are used for measuring 
moderate temperatures : the latter for determining the 
more elevated degrees of heat. 

Liquids are better adapted than either solids or gases for measuring the 
effects of heat by expansion and contraction ; since in solids the direct ex- 
pansion by heat is so small as to be seen and recognized with difficulty, and 
in air or gases it is too extensive, and too liable to be affected by variations 
in the atmospheric pressure. From both of these disadvantages liquids are 
free. 

The liquid generally used in the construction of thermometers is mercury, 
or quicksilver. 

Mercury possesses greater advantages for this purpose than any other 
liquid It is, in the first place, eminently distinguished for its fluidity at all 
ordinary temperatures ; it is, in addition, the only body in a liquid state whose 
variations in volume, or magnitude, through a considerable range of tempe- 
rature are exactly uniform and proportional with every increase and diminu- 
tion of heat. Mercury, moreover, boils at a higher temperature than any 
other liquid, except certain oils; and, on the other hand, it freezes at a lower 
temperature than all other liquids, except some of the most volatile, such as 
ether and alcohol. Thus a mercurial thermometer will have a wider range 
than any other liquid thermometer. It is also attended with this convenience, 
that the extent of temperature included between melting ice and boiling 
water stands at a considerable distance from the limits of its range, or its 
freezing and boiling points. 

119. The Mercurial Thermometer (sec Fig. 30) consists 



Questions. — What is the theory of heat measurement ? What are the instruments for 
measuring heat called ? Why are liquids host adapted for indicating by expansion and 
contraction the effects of heat and cold ? What liquid is generally employed ? What are 
the advantages of mercury for this purpose ? Describe the mercurial thermometer ? 



THE EFFECTS OF HEAT, 



83 



Fig. 30. 



":h 



essentially of a glass tube with a bulb at one 
end, partially filled with mercury. The mer- 
cury, introduced through an opening in the 
end of the tube, is afterward boiled, so as to 
expel all air and moisture, and fill the tube with 
its own vapor. The open end of the tube is 
then closed, by fusing the glass, and as the 
mercury cools it contracts, and collects in the 
bulb and lower part of the tube, leaving a 
vacuum above, through which it may again ex- 
pand and rise on the application of heat. In 
this condition the thermometer is complete, 
with the exception of graduation. 

120. Graduation of Thermometers. — As ther- 
mometers are constructed of different dimensions and capaci- 
ties, it is necessary to have some fixed rules for graduating 
them, in order that they may always indicate the same tem- 
perature under the same circumstances, as the freezing point, 
for example. To accomplish this end the following plan has 
been adopted: — The thermometers arc first immersed in 
melting snow or ice. The mercury will he observed to stop 
in each thermometer-tube at a certain height ; these heights 
are then marked upon the tubes. Now it has been ascertained 
that at whatever time and place the instruments may be af- 
terward immersed in melting snow or ice, the mercury con- 
tained in them will always fix itself at the point thus marked. 
This point is called the freezing point of water. 

Another fixed point is determined by immersing the instru- 
ments in boiling water. It has been found that at whatever 
time or place the instruments are immersed in pure water, 
when boiling, provided the barometer stands at the height of 
thirty inches, the mercury will always rise in each to a certain height. This, 
therefore, forms another fixed point on the scale, and is called the boiling 
point. 

So far as the determination of the boiling and freezing 
points of water are concerned, all the varieties of the mer- 
curial thermometer are constructed alike. The interval, 
however, between these two fixed points is differently di- 
vided in different instruments. 



;->^; r 



Questions. — How are thermometers graduated ' 
alike ? 



In -what respect are all thermometers 



84 



PRINCIPLES OF CHEMISTRY. 



121. Fahrenheit's Thermometer.— In the thermometer 
most generally used in the United States and England, 
and which is known as Fahrenheit's, the interval on the 
scale between the freezing and boiling points, is divided 
into 180 equal parts. This division is similarly continued 
below the freezing point to the place 0, called zero, and 
each division upward from that is marked with the suc- 
cessive numbers 1, 2, 3, etc. The freezing point will now 
be the 32 1 division, and the boiling point will be the 
212th division. These divisions are called degrees, and 
the boiling point will therefore be 212°, and the freezing 
temperature, 32°. 

Thermometers of this character are called Fahrenheit's, from a Dutch phi- 
losophical instrument-maker who first introduced this method of graduation 
in the year 1724. 

" The zero of a thermometric scale has no relation to the real zero of heat, 
or the point at which bodies are entirely deprived of heat. Of this point wo 
know nothing, and there is no reason to suppose we have ever approached it. 
The scale of temperature may be compared to a chain, extended both upward 
and downward beyond our sight. We fix upon a particular link, and count 
upward and downward from that link, and not from the beginning of the 
chain . ' ' — Ge a.ham. 

In indicating thermometrical degrees, the sign — is used to designate those 
below the zero point, in order to distinguish them from degrees of the same 

Fig. 31. name above the zero point. Thus, 32° means 

~ the 32d degree above zero; and —32° the 
32d below zero. 

122. Reaumur and Centigrade 
Thermometers— In addition to Fah- 
renheit's thermometer, two others 
are extensively used, which are 




points of water. 



known as Reaumur's, and the Cen- 
tigrade thermometer, or thermome- 
ter of Celsius. 

The only difference between these three kinds 
of thermometers is the difference in graduating 
tie interval between the freezing and boiling 
Reaumur's is divided into eighty degrees, the Centigrade 



Questions. — Describe the graduation of Fahrenheit's thermometer. What does the 
zero point indicate? IIow are degrees helo-^r zero distinguished ? What other scales are 
used? Describe the graduation of Reaumur ; of Centigrade. 



THE EFFECTS OF HEAT. 



85 



into one hundred, and Fahrenheit's into one hundred and eighty. According 
to Reaumur, water freezes at D , and boils at 80° ; according to Centigrade, 
it freezes at 0°, and boils at 100°; and according to Fahrenheit, it freezes at 
32°, and boils at 212° ; the last, very singularly, commences counting, not 
at the freezing point, but 32° below it.* 

The difference between these instruments can be easily seen by reference 
to Fig. 31. 

In England, Holland, and the United States, the thermometer most gener- 
ally used is Fahrenheit's. Reaumur's scale is used in Germany, and the Cen- 
tigrade in France, Sweden, and some other parts of Europe. The scale of 
the Centigrade is by far the simplest and most rational method of graduation, 
and at present it is almost universally adopted for scientific purposes. 

The scale employed in the present work is that of Fahrenheit's. 

The thermometer was invented about the year 1600 ; but, like many other 
inventions, the merit of its discovery is not to be ascribed to one person, but 
to be distributed among many. 

The variety of circumstances under which thermometers are used, have 
occasioned a considerable variety in their form. The following are some of 
the most important of these modifications. 

123. The SeJf -Registering Thermometer is a form of 
thermometer contrived for the purpose of ascertaining the 
extremes of variation which may occur during a particular 
interval of time ; as in the night. 

Fig. 32. 




It consists of two horizontal thermometers attached to one frame, as is rep- 
resented in Fig. 32, the one, A, containing mercury, and the other, B, spirits 
of wine. On the surface of the mercurial column in the tube is placed a 



* The temperatures expressed by one thermometer scale may be easily reduced to that 
of another, by remembering that 9° of Fahrenheit are equivalent to 5° of Centigrade, or 
4° of Reaumur. In converting Fahrenheit to Eeaumur, or Centigrade, if the degree be 
above the freezing point, 32° must be first subtracted, in order to reduce the degrees of 
the other scales to those of Fahrenheit ; but in the conversion of Reaumur or Centigrade 
to Fahrenheit, S2 3 must be added. 



Questions. — When was the thermometer invented ? What is a self-registering ther- 
mometer ? Describe its construction ? 



PRINCIPLES OF CHEMISTRY. 



pieco of steel- wire, and on the surface of the spirits of wine, a piece of black 
enamel, or ivory. As the spirits contract by exposure to cold, the enamel 
follows it toward the bulb ; but when it expands, the enamel remains sta- 
tionary, and suffers the liquid to pass by it. When the mercury contracts, 
the steel-wire does not follow ; but when the mercury expands, it is forced 
along. Consequently, it remains at the highest temperature. The position, 
therefore, of the two indices will indicate the lowest and highest tempera- 
tures during any given time. A simpler form of thermometer for indicating 
maximum temperature, has been constructed by Messrs. Negretti and Zam* 
bra, of London, and is known by their names. It is merely an ordinary ther^ 
mometer, placed horizontally, with a contraction in the tube just above the 
bulb. "When the mercury expands through heat, the expansive force pushes 
the column past the contraction without difficulty ; but when the temperaturo 
falls, and the expansive force ceases to act, the contraction in the tube pre- 
vents the column from receding. The position of the mercury above the 
contraction indicates, therefore, the highest temperature attained since the 
last observation. The mercurial column is restored to its true place, by a 
slight percussion of the instrument. 

124. The Differential Thermometer is a form of ther- 
mometer so named because it denotes only differences of 
temperature between two substances, or two contiguous 
portions of the same atmosphere. 

•~ oo It consists of two glass bulbs on one tube, bent twice at 

right angles, and supported as represented in Fig. 33. The 
ID 10 kulbs contain air, but the tube is nearly filled with sulphuric 

acid colored red. To one leg of the tube is applied a scale. 
"When the bulbs of this instrument are heated or cooled alike, 
no change will take place in the columns of liquid, because 
the air in both bulbs will undergo an equal expansion or con- 
traction ; but the instant any inequality of temperature exists 
between them, as from bringing a heated substance near to 
one of them, the liquid in the two legs will rise and fail rapidly. 

125. Metallic Thermometer. — A very delicate 
thermometer, known as the metallic, or Brc- 
guet's thermometer, is constructed on the principle of the 
unequal expansion of two metals. 

It consists (see Fig. 34) of two equal strips of platinum and -silver, firmly 
soldered together and coiled in the form of a spiral. One end of the spiral 
is suspended from a fixed point, while the lower end is free and carries an 
index. Variations of temperature cause the two metals to expand and con- 




Qttestions. — What is the thermometer of Negrette and Zamhra ? What is a differential 
thermometer? Describe its construction. Describe the metallic, or Breguet's thermom- 
eter. 



THE EFFECTS OF HEAT. 



87 



Fig. 34. 



tract unequally, and the spiral to twist 
in opposite directions. These mo- 
tions imparted to the index, cause it 
to move over a graduated circle, on 
which degrees are indicated. So sen- 
sitive is this instrument, that when 
inclosed in a large receiver, which was 
rapidly exhausted by an air pump, it 
indicated a reduction of temperature 
from 6 3° to 25°=41°, while a mer- 
curial thermometer fell only to 36°. 

For chemical purposes, thermom- 
eters are sometimes constructed in 
such a way, that the lower part of the 
scale turns up by a hinge, in order .to 
allow the bulb to be immersed in cor- 
rosive liquids. (See Fig. 35.) 

126. Air Thermometers. — 
The first thermometer used consisted of a column of air confined in a glass 




Fig. 36. 




Fig. 35. tube over colored water. Heat ex- 
pands the air and increases the length 
of the column downward, pushing the 
water before it : cold produces a con- 
trary effect. The temperature is thus 
indicated by the height at which the 
water is elevated in the tube. Fig. 36 
represents the principle of the con- 
struction of the air thermometer. 

Fig. 37 represents an air thermom- 
eter filled up with a scale, and termed 

the thermometer of Sanctorius, from its inventor. Fig. 37. 

127. Spirit Thermometers . — As the temperature 
is lowered, the mercury in Fahrenheit's thermometer gradually sinks, 
until it reaches a point 39° below zero, where it freezes. Mercury, 
therefore, can not be made available for measuring cold of a greater 
intensity. This difficulty is, however, obviated by using a thermom- 
eter filled with alcohol colored red, as this fluid, when pure, never 
freezes, but will continue to sink lower and lower in the tube as the 
cold increases. Such a thermometer is called a spirit thermometer. 

128. Pyrometers . — If a Fahrenheit's thermometer be heated, 
the mercury contained in it will rise in the tube until it reaches 660°, 
at which temperature it begins to boil. A slight additional heat 
forms vapor sufficient to burst the tube. Mercury, therefore, can not be used 

QirrsTioxs.— What was the first thermometer used ? How is cold of great intensity in- 
dicated ? How is heat of great intensity measured ? Describe the principle upon which 
the pyrometer is constructed. 



88 



PRINCIPLES OF CHEMISTRY. 



to measure degrees of heat of greater intensity than 660° F. Temperatures 
greater than this are determined by means of the expansion of solids ; and 
instruments founded upon this principle are commonly called pyrometers. 

Fig. 38. 




The principle of the construction of the pyrometer is shown in Fig. 38. 
A represents a metallic bar, fixed at one end, B, but left free at the other, 
and in contact with the end of a pointer, K, moving freely over a graduated 
scale. If the bar be heated by the flame of alcohol, the metal expands, and 
pressing upon tho end of the pointer, moves it, in a greater or less degree. 
In this manner, the effect of heat, applied for a given length of time, to bars 
of different metals, having the same length and diameter, may be determined. 

The pyrometer of practical use is known as Daniel's, and consists of a 
platinum bar inclosed in a tube of black-lead, closed at the bottom. The 
whole is then placed in the fire, or in a mass of melted metal, whose tem- 
perature it is desirable to ascertain. The platinum expands much more than 
the case which incloses it, and projecting upward, moves a lever, which drives 
forward an index over a graduated arc. 

A thermometer does not inform u^5 how much heat any substance contains, 
but it merely points out the difference in the temperature of two or more 
substances. All we learn by the thermometer is whether the temperature 
of one body is greater or less than that of another ; and if there is a differ- 
ence, it is expressed numerically — namely, by the degrees of the thermom- 
eter. It must be remembered that these degrees are part of an arbitrary 
scale, selected for convenience, without any reference whatever to the actual 
quantity of heat present in bodies. 

129. Fluidity as an Effect of Heat,— The first effect 
produced by heat upon solids is expansion. If the heat 
be augmented, they change their aggregate state, and 
melt, or become liquid. Many solids become soft before 
melting, so that they may be kneaded ; for instance, wax, 

Questions.— Describe Daniel' s pyrometer. Does the thermometer inform us how much 
heat a body contains ? After the expansion of bodies by heat, what other effects are next 
©bsarved ? 



THE EFFECTS OF HEAT. 89 

glass, and iron. In this position, glass can be bent and 
molded with facility, and iron can be forged or welded. 

130. Liquefaction. — By liquefaction we understand the 
conversion of a solid into a liquid by the agency of heat, 
as solid ice is converted into water by the heat of the sun. 

The temperature at which liquefaction takes place is called 
the melting point, or point of fusion ; and that at which 
liquids solidify, the freezing point, or point of congelation. 

The melting point of a given solid is always fixed and 
constant, but the degree of heat at which different solids 
melt varies exceedingly. 

Thus, platinum is not melted at 3280° ; iron melts at about 2800° ; lead 
at 612°; wax, 142°; tallow, 92°; olive oil, 3G°; ice, 32°; milk, 30°; oil 
of turpentine, 14°; mercury, — 39°; liquid ammonia, — 46°; while puro 
alcohol, having never been solidified, possesses no known melting point. 

131. Vaporization. — By vaporization is meant the con- 
version of liquid and solid substances into vapor, through 
the agency of heat. Thus water, if heated sufficiently, 
will be converted into steam. It is generally supposed 
that all solid and liquid substances, under the influence of 
a sufficient degree of heat, are susceptible of this change. 

A gas differs from a vapor in the circumstance that it 
is not so easily condensed into a liquid, but permanently 
retains its state under all ordinary conditions of tempera- 
ture and pressure. 

132. Condensation. — If a body in a state of vapor lose 
heat in, sufficient quantity, it will pass into a liquid or 
solid state. Thus, if a certain quantity of heat be ab- 
stracted from steam, it will become water. This change 
is called Condensation. 

The change from a state of vapor to a liquid is termed condensation, be- 
cause, in so doing, the body always undergoes a very considerable diminution, 
of volume, and therefore becomes condensed. 

133. Volatile and Fixed Bodies . — Substances according to the 
facility with which they yield vapor, are said to be volatile, or fixed and non- 

Questions. — What is liquefaction? What is said respecting the melting point of 
bodies? What is vaporization ? How does a gas differ from a vapor ? What is meant 
by the term condensation as applied to vapors ? What is sublimation ? What is the dis- 
tinction between fixed and volatile substances ? 



90 PRINCIPLES OF CHEMISTRY. 

volatile. A volatile substance is one which yields vapor readily by the ap- 
plication of heat, and wastes away on simple exposure to the atmosphere. 
Those substances, on the contrary, are said to be fixed and non-volatile, 
which have little or no tendency to assume the condition of vapor. Thus, 
iron is a fixed substance, because it does not sutler a sensible degree of 
waste when exposed to intense heat. Oils which do not evaporate on simple 
exposure to the atmosphere are also termed fixed, to distinguish them from 
those which yield vapor under the same circumstances. 

The melting of a solid, or its conversion into a liquid, only occurs when the 
solid is heated up to a certain fixed point ; but the conversion of a liquid 
into a vapor takes place at all temperatures. 

Thus, the vapor of water is continually passing off from the surface of the 
soil, from the ocean, and from all animal and vegetable productions. The 
production of vapor also takes place to a very considerable extent from the 
surface of snow and ice, even when the temperature of the air is far below 
the freezing point. 

This circumstance explains the waste of snow and ice which may be ob- 
served during the continuance of severe cold. 

134. Vapors Invisible, — The vapor of water, and all 
other vapors, are invisible and transparent. The water 
which has become diffused through the air by evaporation 
only becomes visible when, on returning to its fluid con- 
dition, it forms mist, cloud, dew, rain, etc. 

Steam, which is the vapor of boiling water, is invisible, but when it cornea 
in contact with air, which is cooler, it becomes condensed into small drops, 
and is thus rendered visible. 

The proof of this may be found in examining the steam as it issues from 
an orifice, or the spout of a boiling kettle : for a short space next to the open- 
ing no steam can be seen, since the air is not able to condense it ; but as it 
spreads and comes in contact with a larger volume of air, the invisible vapor 
becomes condensed into drops, and is thus rendered visible. 

The visible matter popularly called steam, should be, therefore, distin- 
guished from steam proper, or the aeriform state of water. The cloud, or 
smoke-like matter observed, is really not an air or vapor at all, but a collec- 
tion of minute bubbles of water, wafted by a current either of true steam, or, 
more frequently, of mere moist air. 

The surface of any watery liquid, whose temperature is about 20° warmer 
than any superincumbent air, rapidly gives off true steam. It is not neces- 
sary, therefore, for the production of steam, that water should be raised to 
the boiling temperature. 

135. Comparative Volume of Vapors.— Liquids in pass- 

Qtjestions. — Do vapors form at all temperatures ? Are vapors really visible ? Is steam 
invisible ? What is the proof of it ? At what temperature is steam produced *? What is 
the comparative volume of vapors ? 



THE EFFECTS OF HEAT. 91 

ing into vapors occupy a much greater spaca than the sub- 
stances from which they are produced. Water, in passing 
from its point of greatest density into steam, expands to 
nearly 1700 times its volume. 

136. Density of Vapors,— Vapors are of all degrees of 
density. The vapor of water may be as thin as air, or al- 
most as dense as water. 

The subject of vaporization may be considered under two heads, viz., 
evaporation and ebullition. 

137. Evaporation.— "When vaporization takes place only 
from the surface of a body, either because the heat has 
access to that part, or because the evolution of vapor 
takes place through the medium of a gas or air present, 
the action can only be recognized by the diminution of the 
bulk of the body ; this phenomenon is termed Evapora- 
tion. 

138. Ebullition.— When a liquid is heated sufficiently 
to form steam, the production of vapor takes place prin- 
cipally at that part where the heat enters ; and when the 
heating takes place not from above, but from the bottom 
and sides, the steam as it is produced rises in bubbles 
through the liquid, and produces the phenomenon of boil- 
ing, or ebullition. 

Boiling, therefore, may be denned to be the mechanical agitation of a fluid 
by its own vapor. 

139. Boiling Point.— The temperature at which vapor 
rises with sufficient freedom to cause the phenomenon of 
ebullition, is called the boiling point. 

140. Conditions of Evaporation. — Evaporation takes 
place from the surfaces of bodies only, and is influenced 
in a great degree by the temperature, dryness, stillness, 
and density of the atmosphere.* 

* It is a common error that the sun's rays are the first source of evaporation, and many 
persons ignorantly imagine, that because a locality is sunny it is sure to be dry. It can, 
however, be shown, by a great variety of facts, that the wind has more to do with drying 

Questions. — What is said of the density of vapors? In what two ways may liquids be 
vaporized ? What is evaporation ? What is ebullition ? Define boiling and the boiling 
point. What are the conditions of evaporation ? 



92 PRINCIPLES OF CHEMISTRY. 

"When water is covered by a stratum of dry air, the evaporation is rapid, 
even when its temperature is low ; whereas it goes on very slowly if the at-> 
mosphere contains much vapor, even though the air be very warm. 

Evaporation is far slower in still air than in a current. The air imme- 
diately in contact with the water soon becomes moist, and thus a check is 
put to evaporation. But if the air be removed by wind from the surface of 
the water as soon as it has become charged with vapor, and its place sup- 
plied with fresh air, then the evaporation continues on without interruption. 

Air without vapor (theoretically known as dry air) does not exist in na- 
ture, and can not probably be produced by art. 

141. Capacity for Absorption.— Air absorbs moisture at 
all temperatures, and retains it in an invisible state. This 
power of the air is termed its capacity for absorption. 

The capacity of air for moisture increases with the tem- 
perature. 

and evaporation than the sun. In the formation of ice on ponds, for instance, on a windy 
night in extreme winter, nothing is actually gained, since the ice wastes by evaporation 
from the surface as fast as it forms beneath. Every housewife knows that wet linen 
dries more rapidly when flying in the cold wind, than when hanging quietly in the warm 
Bun. The driving blast which accompanies those sudden showers that vex and drench 
travelers in mountain regions, brings an almost instant remedy when the shower has 
passed. Air at rest will take up only a limited quantity of moisture, and is speedily satu- 
rated. But air in motion is never satisfied, and is constantly abstracting moisture from 
the soil. It is not the character of the soil, but the constant and unobstructed motion of 
the air, which reduces open land to barrenness. 

" A proper understanding of the influence which trees and forests have upon the fer- 
tility of a country, by controling the evaporation of moisture from its surface, is of great- 
practical importance. It is matter of surprise to every one who journeys in Syria or 
Greece, that the sacred and classic streams should be of such mean dimensions. Tho 
circumstance, however, finds an explanation in the fact, that the hills of these countries 
have been almost entirely deprived of their forests. And the like cause will everywhere 
produce the like effect. In an open country, the absolute quantity of water which tho 
rivers discharge is not only less than in a wooded country, but the flow is incomparably 
more irregular and unequal. It has been especially noticed in the Western States, that 
since the country has been extensively cleared, the alternations of the ' stage' of water 
in the rivers have been more marked and violent. In New England the effect of an indis- 
criminate clearing away of forests has been practically illustrated by the constant hin- 
derance of mill-streams from drought and freshets. Many water-privileges which, half a 
century ago, were valuable and steady, have now become nearly worthless. The dam 
which was conveniently put up to saw an adjoining forest into profitable plank, now 
that its excellent work is done, will drive the saw in the summer no longer. Many of tho 
larger New England factories have been compelled to introduce steam-power to supply a 
deficiency in the volume of water, which a few yean ago was not troublesome. The cut- 
ting away of forests does not probably diminish the quantity of rain or snow, although 
some authorities maintain that this is the fact ; but it deprives the moisture of its bene- 
ficent effect upon the earth, by causing it lo be too rapidly abstracted — thus producing 
pernicious alternations of freshet and drought, which areas fatal to the health of the soil, 
as to the health of tho men who own the soil." 

Questions. — Does air exist without vapor"? What is understood by the capacity of ab- 
sorption in air ? 






THE EFFECTS OF HEAT 



93 



A volume of air at 32° can absorb an amount of moisture equal to the hun- 
dred and sixtieth part of its own weight, and for every 27 additional degrees 
of heat, the quantity of water it can absorb at 32° is doubled. Thus a body 
of air at 32° F. absorbs the IGOth part of its own weight ; at 59° F., the 80th; 
at 86° F.. the 40th ; at 113° F., the 20th part of its own weight in moisture. 
It follows from this that -while the temperature of the air advances in an 
arithmetical series, its capacity for moisture is accelerated in a geometrical 
series. 

Air is said to be saturated with moisture when it con- 
tains as much of the vapor of water as it is capable of 
holding with a given temperature. 

142. Hy-grom'e-ters. — Instruments designed for meas- 
uring the quantity of moisture contained in the atmos- 
phere, are called Hygrometers.* 

Many organic bodies have the property of absorbing vapor, and thus in- 
creasing their dimensions. Among such may be mentioned hair, wood, whale- 
bone, ivory, etc. Any of these connected with a mechanical arrangement by 
which the change in volume might be registered, would furnish a hygrome- 
ter. The thin, transparent shavings of whalebone, which by bending and 
rolling up when placed upon the warm hand, constitute the p^ 3^ 

so-called sensitive figures, aro illustrations of this prin- 
ciple. 

If we fix against a wall a long piece of catgut, and hang 
a weight to the end of it, it will be observed, as the air 
becomes moist or dry, to alter in length ; and by marking 
a scale the two extremities of which are determined by ob- 
servation when the air is very dry, and when it is saturated 
with moisture, it will be found easy to measure the varia- 
tions. 

143. Hair Hygrometer . — An instrument called 
the " Hair Hygrometer," is constructed upon this principle. 
It consists of a human hair, fastened at one extremity to a 
screw (see Fig. 39), and at the other passing over a pulley, 
being strained tight by a silk thread and weight, also at- 
tached to the pulley. To the axis of the pulley an index 
is attached, which passes over a graduated scale, so that as 
the pulley turns, through the shortening or lengthening of 
the hair, the index moves. When the instrument is in a 
damp atmosphere, the hair absorbs a considerable amount : i 
of vapor, and is thus made longer, while in dry air it be- ' 




* Hygrometer, from the Greek words vypog (moist) and perpov (measure). 



Questions.— When is air said to he saturated with moisture ? What are hygrometers ? 
Explain the hair hygrometer and its principle of construction ? 



94 



PRINCIPLES OP CHEMISTRY. 



comes shorter ; so that the index is of course turned alternately from one side 
to the other. 

The instrument is graduated by first placing it in air artificially made as 
dry as possible, and the point on the scale at which the index stops under 
these circumstances, is the point of greatest dryness, and is marked 0. The 
h} r grometer is then placed in a confined space of air, which is completely 
saturated with vapor, and under these circumstances the index moves to the 
oilier end of the scale : this point, which is that of greatest moisture, is 
marked 100. The intervening space is then divided into 100 equal parts, 
which indicate different degrees of moisture. 



Fig. 40. 




144 Daniel's Hygrometer. — Another 
form of hygrometer, known as "Daniel's Hygrom- 
eter," determines the moisture in the air by indicat- 
ing the dew point, or the temperature at which 
moisture is deposited from the air. It consists of a 
bent tube of glass, Fig. 40, at the extremities of 
which two bulbs, a and b, are blown. The bulb b 
is made of black glass, and contains a little ether, 
into which dips the ball of a small and delicate 
thermometer, contained in the cavity of the tube. 
The whole instrument contains only the vapor of 
ether, the air having been removed. The bulb a is 
covered over with a piece of muslin. The support 
of the tube sustains another thermometer, by which 
we can observe the temperature of the air. When 
an observation is to be made with this instrument, 
a little ether is poured on the muslin of the bulb a; this evaporates rapidly, 
and by so doing reduces the temperature of the other bulb, b. As soon as 
this has cooled sufficiently to condense the moisture of the atmosphere, dew 
will be observed to collect upon it, and the temperature at which the deposi- 
tion takes place is determined by observing the thermometer included in the 
tube. If the air is very moist, it is necessary to cool the bulb b but very little 
before dew is deposited upon it ; if, however, the air is very dry, the cooling 
must be carried to a corresponding lower degree. If the air is perfectly 
saturated, the slightest depression of temperature will cause its moisture to 
precipitate. Knowing, therefore, the temperature of the dew point, we are 
enabled by tables calculated for the purpose, to determine the proportional 
amount of moisture contained in the atmosphere. 

145. Conditions of Ebullition. — Different liquids boil 
at different temperatures, but the boiling point of the 
same liquid is always the same under the same circum- 
stances. The boiling temperature, therefore, constitutes 
a distinctive characteristic of a liquid, and in practical 

Questions. — Describe Daniel's hygrometer. How does the boiling point of liquids vary ? 






THE EFFECTS OF HEAT. 95 

chemistry often affords a ready method of detecting a dif- 
ference in the chemical composition of similar liquids. 

Thus water, under ordinary circumstances, begins to 
boil when it is heated up to 212° F. ; alcohol at 173° ; 
ether at 96° ; syrup at 221° ; linseed oil at 640°. 

146. Salino meter . — "Water containing any dissolved matter boils at a 
higher temperature than when pure — the boiling point on the thermometric 
scale rising in proportion as the amount of matter dissolved in the water in- 
creases. Advantage is taken of this principle in the construction of an instru- 
ment known as the "Salinometer," which is especially used by salt-boilers 
for indicating the quantity of salt held in solution in the water of the boilers. 
It simply consists of a delicate thermometer arranged in connection with the 
interior of the boiler, and by means of a properly graduated scale, the 
percentage of salt held in the water is indicated by the boiling point of the 
water. 

147. Influence of Atmospheric Pressure on Boilin g - 

Liquids, in general, being boiled in open vessels, are subjected to the pressure 
of the atmosphere. The tendency of this pressure is to prevent and retard 
the particles of water from expanding to a sufficient extent to form steam. 
Hence, if the pressure of the atmosphere varies, as it does at different times 
and places, or if it be increased or diminished by artificial means, the boiling 
point of a liquid will undergo a corresponding change. 

The pressure of the atmosphere at the level of the sea is about fifteen 
pounds upon each square inch of surface. It varies occasionally at the same 
place sufficiently to affect the boiling point to the extent of 4A, degrees. 

148. Measurement of Altitudes — As we ascend into the at- 
mosphere the pressure is diminished, because there is less of it above us ; 
it therefore follows, that water at different heights in the atmosphere will boil 
at different temperatures, and it has been found by observation, that an ele- 
vation of 550 feet above the level of the sea causes a difference of one de- 
gree in its boiling point. Hence the boiling point of water becomes an in- 
dication of the height of any station above the sea-level, or in other words, 
an indication of the atmospheric pressure ; and thus by means of a kettle of 
boiling water and a thermometer, the height of the summit of any mountain 
may be ascertained with a great degree of accuracy. If the water boils at 
211° by the thermometer, the height of the place is 550 feet ; if at 210°, the 
height is 1100 feet, and so on, it being only necessary to multiply 550 by the 
number of degrees on the thermometer between the actual boiling point and 
212°, to ascertain the elevation. In the city of Quito, in South America, 
water boils at 194° Fahr.; its height above the sea-level, is, therefore, 9,900 
feet. 

As we descend into mines, the pressure of the atmosphere is increased, there 

Questions. — What influence has the pressure of the atmosphere upon the hoiling 
point? How may the height of mountains be determined by the boiling point of water t 




96 PRINCIPLES OF CHEMISTRY. 

being more of it above us than at the surface of the earth. Water, therefore, 
must bo heated to a higher temperature before it will boil, and it has been 
found that a descent of 550 feet, as before, makes a difference of one- degree. 

Boiling water is, consequently, not equally hot at all places upon the earth, 
and, therefore, not every where alike applicable for domestic purposes. Thus 
at Quito and at the hospital of St. Bernard, in Switzerland, great difficulty 
is experienced in cooking eggs by boiling. 

In a like manner, if by artificial means we increase or diminish the pressure 
of the atmosphere on the surface, of a liquid, we change its boiling point. 
If water be heated in a vacuum, ebullition will commence at a point 140° 
lower than in the open air If a vessel of ether be placed under the receiver 
of an air-pump, and the atmospheric pressure removed from its surface, the 
vapor rises so abundantly that ebullition is produced without any increase of 
temperature. 

149. Pulse-Glass . — This pi'inciple is illustrated by a simple instrument 

p IG 41 called the pulse-glass, Fig. 41, which 

y-^—-^^, consists of a glass tube, c, with bulbs, a 
& ^ofedSifDIn anc * ^ blown upon each extremity; the 

C \||||iF* # ^« w hele is then filled with spirits of wine 

^g^^msrms ^B and its vapor, and hermetically sealed. 

The pressure of the air being thus remc vcd from tho surface of the liquid, 
the heat of the hand upon either bulb is sufficient to cause a violent ebul- 
lition. 

150. Culinary Paradox . — The fact fhat water boils at a reduced 
temperature under diminished pressure, is illustrated by an experiment known 
•is the culinary paradox. A glass flask, containing boiling water is closed 

Fig. 42 tightly with a cork, and then inverted, as in Fig. 42. The 

boiling will instantly cease, owing to the pressure of the 
steam which is formed, upon the surface of tho liquid. If 
we now pour cold water upon the outside of tho flask, tho 
steam within is condensed, and a partial vacuum produced, 
which causes the boiling to recommence with great energy. 
On the other hand, by pouring hot water upon tho outsido 
of the flask, the steam and consequent pressure within is re- 
newed, and the boiling ceases. 

A proof also that steam in escaping from boiling water i3 
obliged to overcome the pressure of the atmosphere, is ob- 
tained by repeating the last experiment with a tin canister 
Instead of a globular glass flask. On corking up tho canister and pouring 
cold water over it, the steam within is suddenly condensed, a vacuum is pro- 
duced, and the canister is instantly crushed in by the pressure of the exter- 
nal air. 



Questions. — How may the boiling point of a liquid be elevated or depressed by artificial 
means ? What is the pulse-glass ? What is the culinary paradox ? What experiment 
proves that steam in escaping is obliged to overcome tho pressure of tbe atmosphere? 







THE EFFECTS OF HEAT. 97 

151. Sugar Boiling . — Several beautiful applications in the arts have 
been made of the principle that liquids boil at a lower temperature when 
irecd from the pressure of the atmosphere than in the open air. 

In the refining of sugar, if the syrup is boiled in the open air, the tempera- 
ture of the boiling point is so high that portions of the sugar become decom- 
posed by tho excess of heat, and lost or injured ; the syrup is therefore boiled 
in close vessels from which the air has been previously exhausted, and in this 
way the water of the sj-rup may be evaporated at a temperature so low as to 
prevent all injury from heat. 

152. Influence of Adhesion on the Boiling Point. — 
Adhesion of the lluid to the surface of the vessel that contains it, has a marked 
effect in raising the boiling point. "Water boils somewhat more readily in a 
metallic vessel than in one of glass. If the interior of a vessel be varnished 
with shell-lac, the boding will not often occur until a temperature of 221° F. 
is reached, and then it wiU take place in bursts, the temperature at each evo- 
lution of vapor falling to 212° F. Boiling can be made to take place steadily 
at 212° in any variety of vessel, by the introduction of a few irregular sub- 
stances, as little fragments of wire, a few pieces of charcoal, etc. The reason 
of this is that in a mass of boiling liquid, the formation of vapor takes place 
principally at the edges of the solid substances with wdrich it may be in con- 
tact ; and the introduction and presence of irregular surfaces thus facilitate 
its formation. 

153. Influence of Air on the Boiling Point ,— Recent 
experiments have shown that the presence of air in solution singularly as- 
sists the evolution of vapor. Air dissolved in water acquires, through the 
agency of heat, a great degree of elasticity, and minute bubbles of it are in 
consequence thrown off in the interior of a boiling liquid, especially where it 
is in contact with a rough surface ; into these bubbles the steam escapes and 
rises. "Water when boiled for a long time is .nearly deprived of air ; and in 
such cases tho temperature has been observed to rise even as high as 260°, 
or 48° above the boding point, in an open glass vessel, which was then shat- 
tered with a loud report by a sudden explosive burst of vapor. In this case, 
the force of cohesion retains the particles of liquid throughout the mass in 
contact with each other, in a species of unstable equilibrium ; and when this 
equilibrium is overturned at any one point, the repulsive power of the excess 
of heat stored up in the mass, suddenly exerts itself, and the explosion is the 
result of the instantaneous conversion of the liquid into vapor. 

The same result takes place when ice, free from air, is melted out of con- 
tact with the atmosphere, as under oil. The temperature of the liquid formed 
gradually rises to about 260° F., when, instead of boiling, it explodes. 

If a single drop of water containing air, be allowed to fall into a mass of 

Qxtestions. — What practical application of these principles has been made in the arts ? 
What influence does adhesion have upon the boiling point ? How may liquids be made 
to boil steadily ? What effect has air dissolved in -water upon the evolution of rapor ? 
What curious experiments illustrate this ? What takes place when ice free from air is 
heated out of contact with air ? 

5 



98 PKINCIPLES OF CHEMISTRY. 

water free from air, which has been heated to a temperature of 250° or 260° F., 
the whole volume instantly becomes agitated in a singular manner, and an ex- 
plosion generally occurs. 

154. Spheroidal State . — "When a drop of water falls upon a sur. 
face highly heated, as of metal, it will be observed to roll aloDg the surface 
without adhering, or immediately passing into vapor. The explanation cf 
this is, that the drop of water does not in reality touch the heated surface, but 
is buoyed up and supported on a layer of vapor which intervenes between 
the bottom of the drop and the hot surface. This vapor is produced by the 
heat which i3 radiated from the hot substance, before the liquid can come in 
contact -with it, and being constantly renewed, continues to support the drop. 
The drop generally rolls because the current of air which is always passing 
over a heated surface drives it forward. The drop evaporates slowly, because 
the layer of vapor between the hot surface and the liquid prevents the rapid 
transmission of heat. The liquid resting upon a cushion of steam continually 
evolved from its lower surface by heat, assumes a rounded, or globular shape, 
as the result of the gravity of its particles toward its own center. 

The designation which has been given to the condition which water and 
other liquids assume when brought in contact with very hot surfaces, is that 
of the " spheroidal state." 

If the surface upon which the liquid rests is cooled down to such an ex- 
tent that vapor is not generated rapidly, and in sufficient quantity to support 
the drop, it will come in contact with the surface, and heat being communni- 
cated by conduction, will transform it instantly into steam. 

This is the explanation of the practice adopted by laundresses of touching 
a flat-iron with moisture to ascertain whether the surface is sufficiently hot. 
If the temperature of the iron is not elevated sufficiently, the moisture wets 
the surface, and is evaporated ; but at a higher degree of temperature, the 
moisture is repelled. 

The phenomenon of the spheroidal condition of water furnishes an explana- 
tion of the feats often performed by jugglers, of plunging the hands with im- 
punity into molten lead, or iron. The hand is moistened, and when passed 
into the liquid metal the moisture is vaporized, and interposes between the 
metal and the skin a sheath of vapor. In its conversion into vapor, the 
moisture absorbs heat, and thus still further protects the skin. 

The bulb of a thermometer plunged into liquids while in the spheroidal 
state, indicates temperatures considerably below the ordinary boiling point. 
Thus Avater in a spheroidal state has a temperature of 205° ; alcohol, 167° ; 
ether, 93° ; sulphurous acid, 13°. When distilled water is allowed to fall 
drop by drop into sulphurous acid in the spheroidal state, the water is in- 
stantly congealed into a spongy mass of ice, even when the containing vessel 
is red hot. 



Questions. — What takes place when a drop of -water falls upon a highly heated surface? 
What is meant by the spheroidal state ? Why can the hand he safely plunged into molten 
iron? What is the temperature of liquids in the spheroidal state ? 



THE EFFECTS OF HEAT, 



99 



155. Distillation, or Sublimation, is a process by which 
one body is separated from another in close vessels, by 
means of heat, in cases where one of the bodies assumes 
the form of vapor at a lower temperature than the other ; 
this first rises in the form of vapor, and is received and 
condensed in a separate vessel. The operation is termed 
Distillation, when the vapor formed condenses into a 
l.quid, and Sublimation when it condenses into a solid. 
The product in the first instance is called a distillate, and 
in the second a sublimate. 

"When the product of one distillation is subjected to further distillations, 
in order to free it to a still greater extent from less volatile substances, the 
operation is called rectification. 

By this means very volatile bodies can be easily separated from less vola- 
tile ones; as brandy and 
alcohol from the less vola- 
tile water which may be 
mixed with them. Water 
of extreme purity can also 
be obtained by distillation, 
because the non-volatile 
and earthy substances con- 
tained in all spring waters 
do not ascend with the va- 
por, but remain behind in 
the vessel. 

Distillation upon a small scale is effected by means of a peculiar-shaped ves- 
sel, called a retort, Fig. 43, which is half filled with a volatile liquid and 




heated; the steam, as it forms, passes 
through the neck of the retort into a glass 
receiver set into a vessel filled with cold 
water, and is then condensed. 

"When the operation of distillation is 
conducted on an extensive scale, a largo 
vessel called a " stilV is used, and, for 
condensing the vapor, vats are con- 
structed, holding serpentine pipes, called 
<; worms," which present a greater con- 
densing surface than if they had passed 
directly through the vat. To keep the 
coil of pipe cool, the vats are kept filled 



Fig. 44. 




Questions. — What is distillntion, or sublimation ? What is the difference between a 
distillate and a sublimate ? What is rectification ? How is distillation effected ? 



100 PRINCIPLES OF CHEMISTRY. 

with cold water. In Fig. 44, a is a furnace, in which is fixed a copper ves- 
sel, or still, to contain the liquid. Heat being applied, the steam rises in the 
head, b, and passes through the worm, d, which is placed in a vessel of water, 
the refrigerator. The vapor thus generated is condensed in its passage, and 
(passes out as a liquid by the external pipe into a receiver. 

156. Drying and Distillation . — The difference between drying 
by heat and distillation is, that in one case, the substance vaporized, being of 
ho use, is allowed to escape or become dissipated in the atmosphene ; while 
in the other, being the valuable part, it is caught and condensed into the 
liquid form. The vapor arising from damp linen, if caught and condensed 
would be distilled water ; the vapor given out by bread while baking, would, 
if collected, be a spirit like that obtained in the distillation of grain. 

157. Latent Heat.— When a solid is converted into a 
liquid, or a liquid into a vapor or gas, heat in large quan- 
tity disappears, and ceases for the time to affect the ther- 
mometer. It is not, however, absolutely lost, but remains 
incorporated with the substance of the liquid, or the gas, 
in an insensible condition. Heat thus disappearing, is 
termed Latent, or Insensible Heat. 

For example, if a thermometer be applied to a mass of snow, or ice just 
upon the point of melting, it will be found to stand at 32° F. If the ice be 
placed in a vessel over a fire, and the temperature tested at the moment it 
has entirely melted, the water produced will have only the temperature of 
32°, the same as that of the original ice. Heat, however, during the whole 
process of melting, has been passing rapidly into the vessel from the fire, and 
if a quantity of mercury, or a solid of the same size, had been exposed to 
the same amount of heat, it would have constantly increased in temperature. 
It is clear, therefore, that the conversion of ice, a solid, into water, a liquid, 
has been attended with a disappearance of heat. 

Again, if a pound cf water at 212° F. be mixed with a pound of water 
at 33° F., we shall obtain two pounds of water at 122°, a temperature ex- 
actly intermediate between the temperature of the two. If, however, a 
pound of ice at 32°, is mixed with a pound of water at 212°, we shall ob- 
tain two pounds of water, of which the temperature is only 51°. In tins 
case the water has lost 161°, while the ice has apparently gained but 19° ; 
go that 142° have disappeared, or become latent. Thus, in order to convert 
a pound of ice at 32° F. into water at 33°, as much heat is required as would*. 
be sufficient to raise 142 pounds of water from 32° to 33° F. Water, there- 
fore, may be regarded as ice in combination with a certain quantity of heat. 



Questions. — What is the difference between drying by beat and distillation ? What 
remarkable circumstance characterizes the phenomena of liquefaction and vaporization ? 
Explain what is meant by latent heat ? What experiments prove that liquefaction occa- 
sions a disappearance of heat '! 



THE EFFECTS OF HEAT. 101 

158. Heat required to Melt Ice. — Some idea of the quantity 
of heat that is required to convert ice into water, without any apparent rise, 
in temperature, may be formed from the fact that the simple conversion of a 
cube of ice, three feet on the side, into water at 32°, would absorb the 
whole amount of heat emitted during the combustion of a bushel of coal. 

159. Disappearance of Heat in Vaporization In the 

conversion of a liquid into gas or vapor, heat disappears to a much greater 
extent than in the conversion of a solid into a liquid. 

The absorption of heat by vaporization, may be easily rendered perceptible 
to the feelings by pouring a few drops of some liquid which readily evapo- 
rates, such as ether, alcohol, etc., upon the hand. A sensation of cold is 
immediately experienced, because the hand is deprived of heat, which is 
drawn away to effect the evaporation of the liquid. On the same principle, 
inflammation and feverish heat in the head may be allayed by bathing the 
temples with any liquid which evaporates easily, as Cologne water, alcohol, 
vinegar, etc. 

A vessel containing water placed over a source of heat which is tolerably 
uniform in temperature, receives equal accessions of heat in equal times. 
The water at first rises steadily in temperature, and at 212° it boils. After 
this, no matter how much the heat is increased, provided the steam be al- 
lowed to escape freely, it becomes no hotter ; all the heat which is added ■ 
serving only to convert the water at 212° into steam or vapor. 

This fact is of considerable importance in domestic economy, and attention 
to it will save much fuel in culinary operations. Soups, etc., made to boil in 
a gentle way by the application of a moderate heat, are just as hot as when 
they are made to boil over a strong fire with the greatest violence. When a 
liquid is once brought to the boiling point, the fire may be reduced,' as a 
comparatively small quantity of heat will be then sufficient to maintain it 
there. 

160. Latent Heat of Steam . — If we immerse a thermometer in 
boiling water, it stands at 212° ; if we place it in steam immediately above it, 
it indicates the same temperature. The question then arises, what becomes 
of all the heat which is communicated to the water, since it is neither indi- 
cated by the water nor by the steam formed from it ? The answer is, that 
it enters into the water and converts it into steam, without raising its tem- 
perature. The proof that steam contains more heat than boiling water, is to 
be found in the fact that if we mix an ounce of water at 212° with five and 
a half ounces of water at 32°, we obtain six and a half ounces of water at 
a temperature of about 60° ; but if we mix an ounce of steam at 212° with 

Qttestioxs. — What is the comparative quantity of heat necessary to convert ice into 
•water ? To what extent is heat rendered latent by vaporization ? What experiments 
prove that heat disappears in vaporization ? Do liquids acquire additional heat after at- 
taining a boiling temperature? What practical application can be made of this principle 
in domestic economy ? What is the sensible heat of steam ? What is its latent heat ? 
How may steam at 212° F. be proved to contain more heat than water at the same tem- 
perature ? 



102 PBINCIPLES OF CHEMISTRY. 

five and a half ounces of water at 32°, we obtain six and a half ounces of 
water at 212°. The steam, from which the increased heat is all derived, 
contains as much more heat than the ounce of water at the same tempera- 
ture, as would be necessary to raise six and a half ounces of water from the 
temperature of 60° to 212°, or six and a half times as much heat as would 
be requisite to raise one ounce of water through about 152° of temperature. 
This quantity of heat will, therefore, be found by multiplying 152° by six 
and a half, which will give a product of 988° — the excess of heat contained 
in an ounce of steam at 212° over that contained in an ounce of boiling 
water at the same temperature. 

In round numbers, therefore, one thousand degrees of heat are absorbed 
in the conversion of water into steam, and this constitutes the latent heat 
of steam. 

The absorption of heat in the process by which liquids are converted into 
vapor, will explain why a vessel containing a liquid that is constantly exposed 
to the action of fire, can never receive such a degree of heat as would de- 
stroy it. A tin kettle containing water may be exposed to the action of the 
most fierce furnace, and remain uninjured ; but if it be exposed, without con- 
taining water, to the most moderate fire, it will soon be destroyed. The 
heat which the fire imparts to the kettle containing water is immediately ab- 
sorbed by the steam into which the water is converted. So long as water 
is contained in the vessel, this absorption of heat will continue ; but if any 
part of the vessel not containing water be exposed to the fire, the metal 
will be fused, and the vessel destroyed. 

161. Effects Produced by the Absorption of Heat. — 
In the conversion of solids into liquids, and of liquids into gases or vapors, 
the heat which disappears is the agent by which liquefaction in the one case, 
and vaporization in the other, are produced ; in other words, the absorption 
of a certain amount of heat is necessary for the production of the change. A 
liquid, therefore, may be regarded as a compound of a solid and heat, and 
a vapor as a compound of heat and the liquid from which it was formed. 

162. Freezing Mixtures. — The absorption of heat con- 
sequent on the conversion of solids into liquids, has been 
taken advantage of in the arts for the production of ar- 
tificial cold ; and the compounds of different substances 
which are made for this purpose, are called freezing mix- 
tures. 

The most simple freezing mixture is snow and salt. Salt dissolved in 
water would occasion a reduction of temperature, but when the chemical re- 
lations of two solids are such, that both by mixing are rendered liquid, a still 

Questions. — Why does a kettle containing water remain uninjured, when exposed to 
the heat of a fire ? What may be considered as the true constitution of liquids and va- 
pors ? What are freezing mixtures ? Why does a mixture of 6now and salt produce a 
high degree of cold ? 



THE EFFECTS OF HEAT. 103 

greater degree of cold is produced. Such a relation exists between salt and 
snow, or ice, and therefore the latter substances are used in preference to 
water. When the two are mixed, the salt causes the snow to melt by rea- 
son of its attraction for water, and the water formed dissolves the salt : so 
that both pass from the sohd to the liquid condition. If the operation is so 
conducted that no heat is supplied from any external source, it follows that 
the heat absorbed in liquefaction must be obtained from the salt 'and snow 
which comprise the mixture, and they must therefore suffer a depression of 
temperature proportional to the heat which is rendered latent. 

In this way a degree of cold equal to 40° below the freezing point of water 
may.be obtained. The application of this experiment to the freezing cf 
ice-creams is familiar to all. 

By mixing snow and sulphuric acid together in proper proportions, a tem- 
perature of from ^0° to 90° below zero can be obtained without difficulty. 

A very convenient process for freezing water without the use of ice is to 
drench finely-powdered sulphate of soda with the undiluted hydrochloric 
(muriatic) acid of the shops. In this way a very low temperature may bo 
readily obtained. The vessel in which the mixture is made becomes cov- 
ered with hoar frost, and water in tubes or bottles immersed in the mixture, 
is speedily frozen. 

163. Greatest Artificial Cold — The most intense artificial cold 
is, however, produced by the rapid evaporation of highly volatile liquids, such 
as result from the condensation and liquefaction of certain gases. By means 
of a mixture of liquid nitrous oxyd and sulphuret of carbon, placed under the 
exhausted receiver of an air-pump, M. Natterer obtained the enormously low 
temperature of two hundred and twenty degrees below zero. 

The cold produced by evaporation is due to the absorption of heat by the 
newly-formed vapor, and the more rapidly evaporation takes place, the more 
rapidly is heat abstracted from the evaporating liquid and from surrounding 
substances. 

164. Freezing by Evaporation . — Ether may be made to evapo- 
rate so rapidly as to freeze water, even in summer. This may be illustrated 
by filling a small glass tube with water, and surrounding it with cotton, or 
some other porous substance, soaked in ether. If a current of air be then 
directed upon the cotton from a common bellows, the ether will evaporate 
and absorb heat so rap- 
idly, as to convert the FiG. 45. 

water into ice in a few <"„ 

minutes. 

165. The C r y - 
oph'o-rus . — An in- 
strument known as the 

Questions. — By what process may water be frozen in summer without the aid of ice? 
What is the most intense artificial cold produced '? "What is the lowest degree of tem- 
perature ever observed ? To what is the cold produced by evaporation due ? How may 
water be frozen by the evaporation of ether ? Explain the action of the cryophorus. 



104 PRINCIPLES OF CHEMISTRY. 

cryophorus, or frost-hearer, strikingly illustrates the production of cold by 
evaporation. It consists of two glass bulbs connected by a tube, and contain- 
ing a portion of water, as represented in Fig. 45. The air is first expelled 
from the instrument by boiling the water inclosed, and allowing the steam 
to escape by a small opening at the extremity of the little projecting tube, e. 
"While the instrument is entirely filled with steam, the point e is fused by 
tho blow-pipe flame, and the opening hermetically closed. In experimenting 
■with this instrument, the water is all poured into one bulb, and the other, or 
empty bulb, is placed in a basin containing a mixture of ice and salt. Tho 
vapor in the cooled bulb is condensed, but its place is immediately supplied 
by vapor' which rises into the vacuum from the water in the other bulb. A 
rapid evaporation, therefore, takes place in the water-bulb, and condensation 
in the empty bulb, until by reason of the condensation and rapid evaporation, 
the water in the former bulb is cooled so low as to freeze. 

Practical Illustrations —A shower of rain cools the air in 
summer, because the earth and the air both part with their heat to promoto 
evaporation. In a like manner, the sprinkling of a hot room with water cools 
it. 

The danger arising from wet feet and clothes is owing to the absorption of 
heat from the body by the evaporation from the surfaces of the wet materials ; 
the temperature of the body is in this way reduced below its natural standard, 
and the proper circulation of the blood interrupted. 

The evaporation which takes place continually from the surface of tho 
skin and the cells of the lungs of animals, is a powerfully cooling agency, and 
a protection against external heat. "When the heat of the body is increased 
by exercise, or by exposure to high temperatures, perspiration and evapora- 
tion take place rapidly. Heat is thereby absorbed and rendered latent in 
large quantity, and a healthy temperature of the system maintained. It is 
on this principle that persons are enabled to expose themselves for a time 
to an atmosphere of very high temperature without serious inconvenience, 
as in foundries, boiler-rooms of steamers, ovens of manufactories, etc. If, 
however, the air be moist, or the surface of the skin be varnished, so as to 
check or prevent perspiration and evaporation, the heat can only be sus- 
tained for a few moments. 

The air in the spring of the year, when the ice and snow are thawing, 
is always peculiarly cold and chilly. This is due to the constant absorption 
of heat from the air by the ice and snow in their transition from a solid to a 
liquid state. 

166. Conversion of Latent into Sensible Ileat.— When 

vapors are condensed into liquids, and liquids are changed 

Questions. — How does a shower of rain cool the air and the earth in summer? How 
does the drainage of a country promote its -warmth ? From what does the danger of wet 
clothes and feet arise? How does perspiration and evaporation from the surface of the 
skin equalize the temperature of the hody ? Why is the air in the spring of the year 
peculiarly cold and chilly ? Under what circumstances is latent converted into sensible 
heat? 



THE EFFECTS OF HEAT. 105 

into solids, the latent heat contained in them is set free, 
or made sensible. 

If water be taken into an apartment whose temperature is several degrees 
bolow the freezing point, and allowed to congeal, it will render the room sen- 
sibly warmer. It is, therefore, in accordance with this principle that tubs of 
water are allowed to freeze in cellars in order to prevent excessive cold. 

The large amount of heat latent in water, which it gives forth as it freezes, 
furnishes a source of heat of the greatest value in mitigating the severity of 
winter, and in rendering the transitions of atmospheric temperature, from heat 
to cold and from cold to heat, uniform and gradual. 

In the colder regions, every ton of water converted into ice gives out and 
diffuses in the surrounding region as much heat as would raise a ton of water 
from 32° to 174° ; and, on the other hand, when a rise of temperature takes 
place, the thawing of the ice absorbs a like quantity of heat: thus, in the one 
case, supplying heat to the atmosphere when the temperature falls ; and, in 
the other absorbing heat from it when the temperature rises. 

In the winter, the weather generally moderates on the fall of snow ; snow 
is frozen water, and in its formation heat is imparted to the atmosphere, and 
its temperature increased. 

Steam, on account of the latent heat it contains, is well adapted for the 
warming of buildings, or for cooking. In passing through a line of pipes, or 
through meat and vegetables, it is condensed, and imparts to the adjoining 
surfaces nearly 1000° of the latent heat which it contained before condensation. 

Steam burns much more severely than boding water, for the reason that 
the heat it imparts to any surface upon which it is condensed, is much greater 
than that of boiling water. 

167. Elastic Force of Vapors.— All vapors are elastic, 
like air. 

The tendency of vapors to expand is generally consid- 
ered to be unlimited ; that is to say, the smallest quantity 
of vapor lias a tendency to diffuse itself through every 
part of a vacuum, be its size what it may, exercising a 
greater or less degree of force against any obstacle which 
may restrain it. 

Recent researches of M. Babinet, a French physicist, seem to show, that all 
gases and vapors entirely lose their elasticity when reduced to a certain de- 
gree of tenuity, and that no gas or vapor, formed under the ordinary pressure 
of the atmosphere, can expand sufficiently to fill an empty space 20,000 times 
greater than the original volume of the gas or vapor. 

Qukstioxs — How does the freezing of water tend to elevate the temperature of the sur- 
rounding atmosphere ? Why is steam well adapted for the warming of buildings and 
for cooking ? Why does steam burn more severely than water of the same temperature f 
What is said of the elasticity of vapors ? In what manner d ) vapors tend to expand? 

5* 



106 PRINCIPLES OF CHEMISTRY. 

The force with which a vapor expands is called its elastic 
force, or tension. 

The elasticity or pressure of vapors is best illustrated in the case of steam, 
which may be considered as the type of all vapors. 

168. Expansive Force of Steam .—When a quantity of pure 
steam is confined in a close vessel, its elastic force will exert on every part 
of the interior of the vessel a certain pressure directed outward, having a 
tendency to burst the vessel. 

"When steam is generated in an open vessel its elastic force must be equal 
to the elastic force or pressure of the atmosphere ; otherwise the pressure of* 
the air would prevent it from forming and rising. Steam, therefore, produced 
from boiling water at 212° F., is capable of exerting a pressure of 15 pounds 
upon every square inch of surface, or one ton on every square foot, a force 
equivalent to the pressure of the atmosphere. 

If water be boiled under a diminished pressure, and therefore at a lower 
temperature, the steam which is produced from it will have a pressure which 
is diminished in an equal degree. If, on the contrary, the pressure under 
which water boils be increased, the boiling temperature of the water and the 
pressure of the steam formed will be increased in a like proportion. "We have, 
therefore, the following rule • — 

Steam raised from water, boiling under any given pres- 
sure, has an elasticity always equal to the pressure under 
which the water boils. 

Steam of a high elastic force can only be made in close vessels, or boilers. 
The water in a steam-boiler, in the first instance, boils at 212°, but the steam 
thus generated being prevented from escaping, presses on the surface of the 
water equally as on the surface of the boiler, and therefore the boiling point 
of the water becomes higher and higher ; or in other words, the water has 
to grow constantly hotter, in order that the steam may form. The steam 
thus formed has the same sensible temperature as the water which produces 
it. 

1G9. Marcet's Digester . — The above principles are experimentally 
proved by means of an apparatus known as Marcet's Digester. This con- 
sists of a stout globular vessel of iron, Fig. 46, into which a portion of mer- 
cury is poured, and then water sufficient to half fill it. Into the top of the 
vessel a long glass tube, b, is tightly fitted, open at both ends, and dipping 
into the mercury. This tube is provided with a scale divided into inches. 
The globular vessel has also two other openings, into one of which a stop- 

Questionb. — What is the force with which a vapor expands termed ? In what manner 
will steam confined in a close vessel exert a pressure ? What is the pressure of steam 
generated in the open air ? What rule governs the elasticity of steam ? What arrange- 
ments are essential to the production of steam of great elastic force ? What relations ex- 
ist between the temperature of steam formed under pressure and the water which pro- 
duces it? What is Marcet's digester? What principles may he experimentally proved 
by this apparatus ? 



THE EFFECTS OF HEAT. 



107 



cock, d, is screwed, and into the other a therniom- Fig. 46. 

eter, c, having its bulb within the globe. Heat is 
applied to the vessel, and the water made to boil. So 
long as free communication with the atmosphere is 
permitted through the open stop-cock d, the tempera- 
ture of ebullition, as indicated by the thermometer, c, 
continues steady at 212°, and the steam formed exerts 
a pressure of course equal to one atmosphere, or 1 5 lbs. 
to the square inch. On shutting the stop-cock, and 
continuing the heat, the temperature of the interior 
rises above 212°. The steam in the upper part of the 
vessel becomes denser, and as fresh portions continue 
to rise from the water, the pressure on the surface of 
the water increases, and this in turn pressing upon the 
mercury, forces it to ascend in the tube. Now the 
height of the mercurial column expresses the elastic 
force or pressure of the steam produced m the boiler 
at any particular temperature above 212°. Thus the 
weight of that section of the atmosphere which presses 
upon the mercury in the open end of the tube is 
equivalent to the weight of a column of mercury of 
30 inches ; and this pressure must be overcome by the 
steam at 212° before it can commence to act upon the 
mercurial guage at all. For every thirty inches after this that the mercury 
is forced up into the tube by the steam, it is said to have the pressure, or 
elastic force of another atmosphere. Thus, when the mercury in the tube 
stands at 30 inches, the steam is said to be of two atmospheres ; at 45 inches, 
of two and a half; at 60 inches, of three atmospheres, and so on. The boil- 
ing point of the water, also, as shown by the thermometer, increases with the 
pressure of the steam upon its surface. "When the mercury stands at 30 
inches, or when the pressure on the water is equal to that of an additional 
atmosphere, the thermometer marks a temperature of 249° ; at 60 inches, 
2*73° ; at 90 inches, or with a pressure of four atmospheres, 291°, and so on. 
170. Tables of the Temperature and Pressure of 
Steam . — As the relation between the temperature and the pressure of 
steam, and the varying temperature at which water boils or gives off steam 
under pressure, are matters of great importance in connection with the steam- 
engine, the French government many years ago appointed a commission of 
eminent scientific men to investigate the whole subject. The result of their 
labors has been embodied in a series of tables, which show at once the pres- 
sure of steam formed in contact with water at any given temperature, or con- 
versely, the temperature at any given pressure. It was thus found that the 
temperature of steam capable of exerting a pressure of twenty five atmos- 




Question. — Under what circumstances were the relations between the temperature and 
pressure of steam investigated? 



108 



PRINCIPLES OF CHEMISTRY. 



pheres, or 375 pounds upon each square inch of boiler surface, was 439°. 
The temperature of the water producing steam of this pressure, must have 
been consequently the same. 

171. Determination of Steam-pressure in Boilers. — 
The application of these principles affords a ready method of determining the 
pressure at any moment which steam exerts upon the interior of a boiler, or 
upon the piston of a steam-engine. Thus, if a thermometer inserted into a 
steam-boiler indicates a temperature of 212° F., we know that the steam ex- 
erts a pressure of one atmosphere, or 15 pounds upon a square inch; if the 
thermometer stands at 249°. the pressure is 30 pounds ■ at 273°, 45 pounds; 
and so on. 

172. Barometer Guage . — The degree of pressure which steam ex- 
erts upon the interior of the boiler is, however, more generally determined by 
the height to which a column of mercury is elevated and sustained by such 
pressure. The instrument employed for this purpose is termed a " steam" or 



Fig. 47. 




"barometer guage." It consists simply 
of a bent tube, A, C, D, E, Fig. 47, fitted 
into the boiler at one end, and open to 
the air at the other. The lower part of 
the bend of the tube contains mercury, 
which, when the pressure of steam in 
the boiler is equal to that of the external 
atmosphere, will stand at the same level, 
H, R, in both legs of the tube. When 
the pressure of the steam is greater than 
that of the atmosphere, the mercury is 
depressed in the leg C D, and elevated in 
the leg D E. A scale, G, is attached to 
the long arm of the tube, and by observ- 
ing the difference of the levels of the mer- 
cury in the two tubes, the pressure of the steam may be calculated. Thus, 
when the mercury is at the same level in both legs, the pressure of the 
steam balances the pressure of the atmosphere, and is therefore 15 pounds 
per square inch. If the mercury stands 30 inches higher in the long arm 
of the tube, then the pressure of the steam is equal to that of two atmos- 
pheres, or is 30 pounds to the square inch, and so on. 

173. Varying Conditions of Steam-pressure .—It is to bo 
understood that the relations between the pressure of steam and its tempera- 
ture which have been pointed out, exist only when the steam is in contact 
with a body of water from which fresh steam is constantly rising, as in an 
ordinary steam-boiler. Under such circumstances, the elasticity, or expansive 
force of the steam, increases rapidly with its increase in temperature, but in 

Questions. — How may the pressure of steam upon the interior of a boiler be deter- 
mined by means of the thermometer? What is a barometer guage? Under -what cir- 
cumstances do the relations which have been pointed out between the pressure of steam 
and its temperature exist ? In what manner does steam heated apart from water expand ? 



THE EFFECTS OF HEAT. 109 

a greater degree by equal additions of heat at high, than at low temperatures. 
If, however, the steam is heated apart from water, it follows the law that 
regulates the expansion of all gaseous bodies, viz., that equal increments of 
heat expand it equally at all temperatures — this expansion being equal to 
l-490th of its volume at 32° F. for every additional degree of heat imparted to 
it* 

174. High-pressure Steam.— Steam generated by water 
boiling at a very high temperature, is known as high- 
pressure steam. By this we mean steam condensed, not 
by the withdrawal of heat, but by pressure, just as high- 
pressure air is merely condensed air. To obtain double, 

* Some very curious experiments which have heen made from time to time, seem to 
show that steam and other vapors, when subjected to extraordinary pressure, do not con- 
tinue to expand with additions of heat, but actually contract. The first information which 
was obtained in relation to this subject was from a very dangerous experiment tried many 
years since in England. A measured quantity of water was placed in a boiler, with all 
the safety-valves most carefully closed, and every chance for the escape of steam pre- 
vented. The fire was now got up, and for some time the steam-guage, as usual, indicated 
a regularly increasing pressure. At length, however, to the surprise of all, the pressure 
was seen slowly but gradually to diminish, and although the boiler-plates became nearly 
red-hot, this remarkable phenomenon continued, and when the boiler had cooled, it was 
found that no water had escaped. 

The experiment was afterward repeated by De la Tour, a French chemist, in a different 
manner with similar results. He partially filled some very strong glass tubes with water, 
alcohol, ether, and some other liquids, furnished them with guages, and hermetically 
sealed them. The tubes were then gradually exposed to heat, until the contained liquids 
vaporized, and as true steam became transparent, or invisible. Under these circum- 
stances, the law " that the elasticity or expansive force of vapors augments with every ad- 
ditional increase of temperature," was not found to hold good, and the following results 
were obtained : 

All the liquids, by reason of the enormous pressure which the vapor gradually formed 
from them exerted upon their surfaces, required to be elevated to a high degree of tem- 
perature before complete vaporization took place. Ether, which passes into vapor in the 
open air at a temperature of 96-* F., only became vapor at 328°, in a space equal to 
double its original bulk ! At this temperature its vapor should, according to the recog- 
nized law of expansion, have exerted a pressure of 209 atmospheres, or more than 3,000 
pounds per square inch • it, however, exerted a pressure of only 37 atmospheres, or 555 
pounds per square inch. Alcohol, which occupied 2-Sths the capacity of its tube, gradu- 
ally expanded to double its volume, and then suddenly disappeared in vapor, at a tem- 
perature of 404° F. ; its calculated pressure was 3,600 pounds per square inch ; its real 
pressure was only 1,700 pounds. Water was found to become vapor in a space equal to 
about four times its original bulk, at a temperature of about 773°. At this temperature 
its solvent power was so greatly increased, that it acted most powerfully upon the glass 
and broke it, and it was found necessary to add carbonate of soda to the water to diminish 
its action. As the vapors in the tubes cooled, a point was observed at which a sort of 
cloud filled the tube, and in a few moments after, the liquid suddenly re-appeared. 

In explanation of the diminished pressure which vapors of high temperature exert un- 
der the above-mentioned conditions, it has been suggested that their particles, by reason 
of their forced and close contiguity, are partially controlled by a force of cohesion, which 
in part neutralizes the expansive force imparted by the heat. 

Question. — What is high-pressure steam ? 



110 PRINCIPLES OF CHEMISTRY. 

triple, or greater pressure of steam, we must have twice, 
thrice, or more steam under the same volume. 

175. Super- heated Steam.— Steam which has been heated 
in a separate state to a high degree of temperature is 
known as super-heated steam. In this condition it is em- 
ployed for the production of effects not attainable by the 
use of ordinary steam ; such as the distillation of oils, 
the carbonization of wood, etc. 

In some of the processes recently introduced for the distillations of oils by 
the use of super-heated steam, the temperature of the steam is elevated to a 
sufficient degree to melt lead. To effect the carbonization of wood, steam is 
elevated to a high degree of temperature by passage through red-hot pipes. 
It is then allowed to enter a vessel containing wood which is intended to be 
converted into charcoal. The heated steam penetrating into the pores of 
the wood, drives off the volatile portions, the water, tar, etc., and leaves the 
pure carbon behind. 

In the manufacture of lard on an extensive scale, the carcase of the whole 
hog is exposed to the action of steam at a very high pressure and tempera- 
ture. This acting upon the mass of flesh, breaks up and reduces the wholo 
to a fat fluid mass, leaving the bones in the state of powder. Steam of or- 
dinary pressure and temperature, under the same circumstances, would not 
produce this effect. 

176. Vapor produced by different Liquids.— Equal bulks 
of different liquids raised to their respective boiling points, 
produce very different quantities of vapor. 

Water furnishes, bulk for bulk, a much larger amount of vapor than any 
other liquid; a cubic inch of water at its ordinary boiling point, 212°, ex- 
panding to nearly a cubic foot of steam at 212°, or to about 11 00 times its 
volume ; a cubic inch of alcohol, on the other hand, at its ordinary boiling 
temperature, expands only 528 times its volume; ether to 298; and oil of 
turpentine to 193. 

177. Ratio between Sensible and Latent Heat. — The 
sum of the sensible heat of steam, and the quantity of 
latent heat contained in it, are always the same, since the 
latent heat of steam diminishes exactly in proportion as 
its sensible heat rises. 

"Water may be easily made to boil in a vacuum at the temperature of 100°, 

Questions. — What is super-heated steam ? For what purposes is it applied ? How can 
wood be carbonized by the use of steam ? How is high-pressure steam employed in the 
manufacture of lard? Is the quantity of vapor produced from equal bulks of liquid the 
same ? What are illustrations of this ? What ratio exists between the sensible and lat- 
ent heat of steam ? Is there any economy in evaporating water at a low temperature and 
under diminished pressure ? 



THE EFFECTS OF HEAT. Ill 

but the steam generated is much less dense than that produced at 212° 
and has a greater latent heat. If water boils at 312°, the amount of heat 
absorbed (rendered latent) in vaporization, will be less by 100° than if it had 
boiled at 212° ; and, on the contrary, if water be boiled under a diminished 
pressure, at 112°, the heat absorbed in vaporization will be 100° more than 
if it had boiled at 212°. Hence there can be no economy of heat in distilling 
in vacuo. 

The sum cf the sensible and latent heat of steam being always the same, 
1184°, wo may very readily ascertain the latent heat of steam at any tempe- 
rature, by subtracting its sensible heat from this constant number. For ex- 
ample, steam at 280° has a latent heat of 904° (1184-280=904); so also 
steam at 100° has 1084° of latent heat. 

The theory of latent heat, and the principles which govern the formation, 
expansion, and condensation of vapors, are practically applied in the working 
of the steam-engine, and in many industrial operations. A further considera- 
tion of them is, however, foreign to the object of this work. 

178. Liquefaction of Gases.— Gases were formerly con- 
sidered to be essentially different in their nature from va- 
pors, but comparatively recent experiments have shown 
that their constitution is similar, and is owing to the latent 
heat they contain. 

Faraday demonstrated the possibility, by the joint action of cold and great 
pressure, of reducing several of the so-called permanent gases to the liquid 
and even to the solid state. 

The method employed by him was Fia. 48. 

to generate the gas from materials 
placed in one end of a strong glass 
tube, bent in the middle, and her- 
metically sealed, as represented in 
Fig. 48. The gas, accumulating in a 
confined space, exerts an enormous pressure in virtue of its expansive force ; 
the effect of which is, that a portion of the gas itself condenses into a liquid 
in the end of the tube most remote from the materials, which is kept cool by 
immersion in a freezing mixture. This experiment is a somewhat hazardous 
one, from the liability of the tube to burst under the pressure exerted, and the 
hands and face of the operator should always be protected by gloves and a 
mask of wire gauze. In this way chlorine, cyanogen, carbonic acid, and sev 
cral other gases, may be liquefied. 

By means of an apparatus of different construction, but involving the same 
principle, carbonic acid gas can be liquefied and solidified in large quantities. 
The details of this process will be described under the chemical consideration 
of this substance. 

Questions. — How may the latent heat of steam he calculated? To what do gases 
and vapors undoubtedly owe their constitution ? Who first liquefied gases ? By what 
means was this accomplished ? What gases were thus liquefied ? 




112 PRINCIPLES OF CHEMISTRY. 

Some of the gases are liquefiable with much greater facility than others, and 
a few assume a liquid or solid form by the mere application of cold, as sul- 
phurous acid gas. Others have resisted all attempts to reduce them to a 
liquid state by subjection to immense pressure aided by the greatest artificial 
cold. Among these are oxygen, hydrogen, nitrogen, carbonic oxyd, coal gas, 
etc. Oxygen remained gaseous under a pressure of over 900 pounds to the 
square inch, and at a temperature of 140° below zero. 

179. Absorption of Gases by W ate r . — All gases are absorbed 
or condensed by water in a greater or less degree, in which case they must 
certainly assume the liquid form. The quantity absorbed is very different for 
different gases ; and in the same gas the quantity absorbed depends upon the 
pressure to which the gas is subjected, and the temperature of the water. 
The colder the water, the greater the quantity of the gas taken up and re- 
tained by it. 



X 



CHAPTER III 

LIGHT. 



180. Light and its Chemical Relations,— The general 
consideration of the laws of light belongs to the science of 
Optics, a department of Natural Philosophy. Light, how- 
ever, is an important agent in producing chemical changes, 
especially in the organized forms of matter ; while the 
physical characters of an object, revealed by the mere me- 
chanical action of light on its structure, are often of the 
greatest chemical value. 

A brief reference to some of the more important laws and physical prop- 
erties of light, constitutes a proper introduction and preparation for the study 
of its chemical effects. 

SECTION I. 

NATURE AND SOURCES OF LIGIIT. 

181. Nature of Light,— Of the real nature of light we 
know nothing. Two theories or hypothesis, however, have 
been proposed to account for its phenomena, which are 

Questions. — Are all gases reduced with equal facility? What gases have resisted all 
attempts to liquefy them ? What is said of the absorption of gases by water ? What 
connection is there between light and chemistry ? What do we know respecting the real 
nature of light ? 



NATURE AND SOURCES OF LIGHT. 113 

known as the Corpuscular, or Emission theory, and the 
Undulatory theory. 

182. The Corpuscular Theory supposes the sensation of 
light to be occasioned by the transmission of particles of 
a refined species of matter from the luminous body to the 
eye. 

According to this theory, there is a striking analogy or resemblance be- 
tween the eye and the organs of smelling. Thus, we recognize the odor of 
an object in consequence of the material particles which pass from the object 
to the organs of smelling, and there produce a sensation. In the same 
manner, a visible object at any distance may be supposed to send forth parti- 
cles of light, which move to the eye and produce vision, by acting mechan- 
ically on its nervous structure, as the odoriferous particles of a rose produce a 
sensible effect upon the organs of smell. 

183. The Undulatory Theory supposes that all space, 
and the interstices of all material objects, are pervaded by 
an elastic medium, or ether, of inconceivable tenuity. 
This medium is not light itself, but is susceptible of being 
thrown into vibrations or undulations by impulses inces- 
santly emanating from all luminous bodies. These, reach- 
ing the eye, affect the optic nerve, and produce the sen- 
sation which we call light. 

According to this theory, there is a striking analogy between the eye and 
the ear ; the vibrations, or undulations of the ethereal medium being supposed 
to pass along the space intervening between the visible object and the eye, in 
the same manner as the undulations of the air, produced by a sounding body, 
are transmitted to the ear. 

The corpuscular theory was sustained by Newton, and was for a long time 
generally believed. Since the commencement of the present century, how- 
ever, it has been gradually losing ground, and recent experiments instituted 
Dy MM. Foucault and Fizeau, of France, conclusively demonstrate its incor- 
rectness. It is now, therefore, entirely discarded by all the leading scientific 
authorities, and the undulatory theory is received as substantially correct — 
since it affords the most complete explanation of the facts upon which the 
science of optics is based. The language, however, which is generally em- 
ployed in describing optical phenomena is for the most part framed in ac- 
cordance with the corpuscular theory. 

184. Sources of Light. — The great natural sources of 

Questions. — Explain the corpuscular theory of light. "What analogy does this theory 
present? Explain the undulatory theory. What analogy, according to this theory, exists 
between the eye and the ear ? Which theory is generally received ? What are the sources 
of light ? 



114 PRINCIPLES OF CHEMISTRY. 



light are the sun and the heavenly bodies. All bodies 
when heated to a sufficient degree become luminous. 

All solid bodies begin to emit light in the daytime at the same temperature, 
viz., 9*77° of Fahrenheit's thermometer. As the temperature rises, the bril- 
liancy of the light rapidly increases, so that at a temperature of 2600° it is 
almost forty times as intense as at 1900°. Gases must be heated to a much, 
greater extent before they begin to emit light. 

185. Electric Light.— The most splendid artificial light 
known is developed through the agency of electricity. 

The electric light, so-called, is produced by fixing pieces of pointed char- 
coal to the wires connected with opposite poles of a powerful galvanic bat- 
tery, and bringing them within a short distance of each other. The space 
between the points is occupied by an arch of flame that nearly equals in daz- 
zling brightness the rays of the sun. 

186. Phosphorescence .—The term phosphorescence is applied to 
that property which various bodies possess, of emitting a feeble light at ordi- 
nary, or low temperatures. 

Phosphorescence was formerly supposed to be due to the presence of phos- 
phorus (an elementary substance which emits light in the dark). Hence the 
origin of the name. The phenomenon is now known to proceed from other 
agencies. 

A great number of bodies possess the property of shining in the dark when 
they have been previously exposed to the light of the sun. Oyster shells 
which have been ignited and cooled, especially exhibit phosphorescence. 
Among other substances which are often luminous in the dark, are white 
paper (especially when it has been heated nearly to burning), egg-shells, 
corals, bones, ivory, leather, and the skins of men and animals. The cause 
of this phenomenon is, probably, that the bodies by being exposed to light, 
absorb a portion of it unaltered into their substance by adhesion, and subse- 
quently give it out in a dark place. — G-melin. 

The phenomenon of phosphorescence occurs in the most marked degree 
in living organized bodies. The glow-worms, and several species of flies and 
beetles, have the power of emitting from their bodies a beautiful pale, bluish 
white light. The great lantern-lly of South America is especially brilliant — 
a single insect affording sufficient light to enable a person to read. The 
appearance of vast luminous tracts in the sea, at night, is a well-known phe- 
nomenon. This was formerly ascribed to the motion of the waves, to elec- 
tricity, or to the formation of gases containing phosphorus, through the pu- 
trefaction of marine animals ; but it is now generally believed to be due to 
the presence of an immense number of phosphorescent animalcuke. 

Questions. — At what temperature do solids become luminous? How is the most splen- 
did artificial light produced ? "What is phosphorescence ? Under what circumstances do 
bodies often become luminous ? How is the phenomenon accounted for ? What substances 
exhibit phosphorescence in the most marked degree ? What arc remarkable instances 
of phosphorescence in the animal kingdom ? To what is the luminous appearance of the 
6ea due ? 



NATURE AND SOURCES OF LIGHT. 115 

Sea-fisli, in general, soon after death exhibit a luminous appearance, par- 
ticularly the herring and the mackerel. The light is most intense before 
putrefaction commences, and gradually disappears as decomposition proceeds. 
In order to observe the phenomenon more distinctly, the fish should be gut- 
ted, and the roes and scales removed. By placing such luminous fish also 
in weak saline solutions, such as those of Epsom salts or common salt, the 
solutions even become luminous, and the appearance continues for some days ; 
it; is particularly noticeable when the liquids are agitated. The light is quickly 
extinguished by the addition of pure water, of lime water, and by acids in 
general. 

The decay of wood, when the temperature is moderate and moisture and 
a small quantity of air are present, is frequently attended with an evolution 
of light. Wood exhibiting this appearance is familiarly known as " light 
wood" and is of a white appearance. When wood decays in the presence of 
much moisture and a free access of air, it is reduced to a brown pulverulent 
mass which is not luminous. The phosphorescence of wood ceases when the 
temperature falls as low as 42° E., and it is also irrecoverably destroyed by 
the action of boiling water. 

The cause of phosphorescence is not fully understood , it is, however, be- 
lieved to be the result ol a chemical action between the oxygen of too air, 
or water, and the so-called phosphorescent a matter, This matter is capable 
of separation from the living -animal, and is characterized by a remarkable and 
disagreeable odor. 

Light is also developed, under certain circumstances, in 
the act of crystallization. 

If the process of crystallizing certain substances be watched in a darkened 
room, the separation of each crystal will be observed to be accompanied with 
a faint flash of light. 



SECTION II. 

PROPERTIES OF LIGHT. 

187. Propagation of Light . — Light, from whatever source 
it may be derived, moves in straight lines, or rays, so long- 
as the medium traversed is uniform in density. 

By a medium, we mean the space or substance through which light passes. 
In taking aim with a gun or arrow, we proceed upon the supposition that 
light moves in straight lines, and try to make the projectile go to the desired 
object as nearly as possible by the path along which the light comes from the 
object to the eye. 

Questions. — What circumstances attend the decomposition of sea-fish ? What is said 
of the luminosity of decayed wood? What is the supposed cause of phosphorescence? 
Is light ever developed by the act of crystallization ? In what manner is light propagated ? 



116 PRINCIPLES OF CHEMISTRY. 

Thus, in Fig. 49, the line A B, which represents the line of sight, is also 
the direction of a line of light passing in a perfectly straight direction from the 
object aimed at to the eye of the marksman. 

Fig. 49. 



188. Divergence of Light. — Kay s of light proceeding from 
a luminous body diverge, or spread out from one another 
in every direction. 

189. Law of Diminution of Light by Distance.— When 
light diverges from a luminous center, its intensity dimin- 
ishes, not according to the distance, but as the square of 
the distance.* 

Thus, at a distance of two feet, the intensity of light will be one fourth of 
what it is at one foot ; at three feet the intensity will be one ninth of what it 
is at one foot. In other words, the amount of illumination at the distance of 
one foot from a single candle would be the same as that from four, or nine 
candles at a distance of two, or three feet, the numbers four and nine being 
the square of the distances two, and three, from the center of illumination. 

190. Velocity of Light. — Light does not pass instanta- 
neously through space, but requires for its passage from 
one point to another a certain interval of time. 

The velocity of light is at the rate of about one hun- 
dred and ninety-two thousand miles in a second of time. 

191. Action of Light on Matter. — When light falls upon 
any object, it may be disposed of in three ways ; 1st, it 
may be bent back, or reflected ; 2d, it may be absorbed 
into the substance of the body, and disappear ; or 3d, it 
may be transmitted, or pass through the body. 



* It is an exceedingly curious fact, that this law of the variation of influence according 
to the square of the distance, applies to all physical forces which spread or radiate from a 
center, such as gravitation, heat, light, electricity, magnetism, and sound. 

Questions. — What is meant by the divergence of light? How does tin intensity of 
light diminish by distance ? Illustrate this law. What is the velocity of light ? How is 
light falling upon the surface of a body disposed of? 



PROPERTIES OF LIGHT. 117 

When the portion of light reflected from any surface, or 
point of a surface, to the eye is considerable, such surface, 
or point, appears white ; when very little is reflected, it 
appears dark-colored ; but when all, or nearly all the rays 
are absorbed, and none are reflected back to the eye, the 
surface appears black. 

192. Transparent and Opaque Bodies.— Bodies which 
allow the light which falls upon their surfaces to pass 
through them, are said to be transparent ; while those 
which prevent its passage are said to be opaque. 

193. Luminous Bodies are those which shine by their 
own light ; such, for example, as the sun, the flame of a 
candle, metal rendered red hot, etc. 

All bodies not in themselves luminous, become visible 
by reflecting the rays of light. X 

194. Law of Reflection of Light.— The law which gov- 
erns the reflection of light is exceedingly simple, and is 
the same as that which governs the motion of an elastic 
body thrown against a hard, smooth surface. If the light 
falls perpendicularly upon a flat surface, it is turned back, 
or reflected perpendicularly, and in the same lines ; if it 
falls obliquely, it is reflected obliquely, the angle of in- 
cidence being equal to the angle of reflection. 

Thus, in Fig. 50, let A B represent the direction of an incident ray of light 
falling on a mirror, F C. It will be reflected in the direction B E. If we 
draw a line, D B, perpendicular to the surface of the mirror, at the point of 
reflection, B, it wfll be found that the 
angle of incidence, A B D, is precisely 
equal to the angle of reflection, E B D. 
If the light falls perpendicularly upon tho 
surface, F C, as in the direction D B, it 
will be reflected in the same line, B D ; 
or in other words, the incident and re- 
flected ray will coincide. 

The same law holds good in regard to 
every form of surface, curved as well as plane, since a curve may be supposed 
to be formed of an infinite number of little planes. 

Questions. — When is a body light-colored, and -when dark? What are transparent 
and opaque bodies ? What are luminous bodies ? How are bodies not luminous ren- 
dered visible ? What is the law cf the reflection of light ? 




118 



PRINCIPLES OF CHEMISTRY. 



195. Refract ion. —When a ray of light falls perpen- 
dicularly upon the surface of an uncrystallized transparent 
substance of uniform density, it continues on its course 
unchanged ; but if it falls upon the surface obliquely, its 
direction is suddenly changed as it enters the transparent 
object, or medium ; it then passes on in its new direction 
in a straight line, and on quitting the medium, it is again 
abruptly bent back to its original course, provided the 
surface of entrance and the surface of exit be parallel to 
each other. Such a change in the course of a ray of light 
is termed Refraction. 

When the ray of light passes from a rarer to a denser medium (as from air 
into glass or water), the ray is bent or refracted toward a line perpendicular 
to that point of the surface on which the light falls ; when, on the contrary, 
the ray passes from a denser to a rarer medium, the ray is bent in the opposite 
direction, or from the perpendicular. 

p IG 51> Thus, in Fig. 51, suppose n m to represent tho 

surface of water, and S a ray of light striking 
upon its surface. "When the ray S enters tho 
water, it will no longer pursue a straight course, 
but will be refracted, or bent toward the perpen- 
dicular line, A B, in the direction H. The denser 
the water or other fluid may be, the more the ray 
S OH will be refracted, or turned toward A B. 
If, on the contrary, a ray of light, H 0, passes from 
the water into the air, its direction after leaving the water will be further 
from the perpendicular A B, in the direction S. 

A straight stick, partly immersed in water, appears to be broken or bent 
at the point of immersion. This is owing to the fact that the rays of light 
proceeding from the part of the stick contained in the water are refracted, or 
caused to deviate from a straight line as they pass from tho 
water into the air ; consequently that portion of the stick 
immersed in the water will appear to be lifted up, or to 
be bent in such a manner as to form an angle with the 
part out of the water. 

The bent appearance of the stick in water is represented 
in Fig. 52. For the same reason, a spoon in a glass of 
water, or an oar partially immersed in water, always ap- 
pears bent. 




Fig. 


52. 






gs 













QtrrsTiONS. — "What is understood by the refraction of light ? "When will a ray of light 
be transmitted through a transparent substance without refraction ? In what manner is 
a ray of light refracted in passing from a rarer to a denser medium, and in the reverse 
direction ? "What familiar fact illustrates this principle ? 



PROPERTIES OF LIGHT. 119 

196. Variations of Refractive Power. — No law has yet 
been discovered which will enable us to judge of the re- 
fractive power of bodies from their other qualities. As a 
general rule, dense bodies have a greater refractive power 
than those which are rare ; and the refractive power of any 
particular substance is increased or diminished in the same 
ratio as its density is increased or diminished. 

Refractive power seems to be the only property, except weight, which is 
unaltered by chemical combination ; so that by knowing the refractive power 
of the ingredients, we can calculate that of the compound. 

All highly inflammable bodies, such as oils, hydrogen, the diamond, phos- 
phorus, sulphur, amber, camphor, etc., have a refractive power from ten to 
seven times greater than that of incombustible substances of equal density. 

Of all transparent bodies the diamond possesses the greatest refractive or 
light-bending power, although it is exceeded by a few deeply-colored, almost 
opaque minerals. It is in part to this property that the diamond owes its 
brilliancy as a jewel 

Many years before the combustibility of the diamond was proved by ex- 
periment, Sir Isaac Newton predicted, from the circumstance of its high re- 
fractive power, that it would ultimately be found to be inflammable. 

The determination of the refracting power of a body is often a valuable 
guide in estimating its chemical purity. The adulteration of essential oils 
may in this way be often detected with ease, when it would be otherwise 
difficult to ascertain it. Thus genuine oil of cloves has a refractive power 
expressed by the numbers 1,535, while that of an impure and adulterated 
specimen was not more than 1,498. 

197. Double Refraction is a property which certain 
transparent substances possess, of causing a ray of light in 
passing through them to undergo two refractions ; that 
is, the single ray of light is divided into two separate rays. 

A very common mineral called " Iceland spar," -p IG 53 

which is a crystallized form of carbonate of lime, is 
a remarkable example of a body possessing double 
refracting properties. It is usually transparent and 
colorless, and its crystals, as shown m Fig. 53, have 
the geometrical form of a rhomb, or rhomboid ; — this 
term being applied to a solid bounded by parallel 
faces, inclined to each other at an angle of 105°. 

Questions. — What estimate can we form of the refractive power of a body from its other 
qualities'? What is the refractive property of inflammable substances ? What transpa- 
rent substance possesses the greatest refractive power ? How may refraction be used 
for determining the chemical purity of a substance ? What is an illustration of this f 
Whaf is double refraction? What substance possesses doubly refracting powers in a re- 
markable degree ? 




120 



PRINCIPLES OF CHEMISTRY. 




The manner in which a crystal of Iceland spar divides a ray of light into 
two separate portions is clearly shown in Fig. 54 ; in 
which S T represents a ray of light, falling upon a sur- 
face of a crystal of Iceland spar, A D E C, in a perpen- 
dicular direction. Instead of passing through without any 
refraction, as it would in case it had fallen perpendicu- 
larly upon the surface of glass, the ray is divided into 
two separate rays, the one, T 0, being in the direction of 
the original ray, and the other, T E, being. bent or re- 
fracted. The first of these rays, or the one which follows 
the ordinary law of refraction, is called the " ordinary" 
ray ; the second, which follows a different law, is called 
the " extraordinary" ray. 
If we look at an object, as a dot, a letter, or a line, through a plate of glass 
Fig. 55. it appears single ; but if a double re- 

fracting substance, as a plate of Ice- 
land spar, be substituted, a double 
image will be perceived, as two dots, 
two letters, two lines, etc. This re- 
sult of double refraction is represented 
in Fig. 55. 

The phenomenon of double refrac- 
tion is due entirely to the peculiar 
molecular structure of the medium through which the light passes. This is 
proved by taking a cube of regularly annealed glass, which produces but one 
refracted ray, and heating it unequally, or subjecting it to pressure : a change 
is thereby effected in the arrangement of its parts, and double refraction takes 
place. 

The diamond may be distinguished from all other precious stones, with a 
single exception (the garnet), by having only a single refraction, the others 
possessing double refraction, or giving a double image of a taper or small 
light viewed through their faces. By the same means all precious stones, ex- 
cept diamond and garnet, may be distinguished from artificial ones, by the 
former having double refraction, and the latter only single refraction. 

198. Polarization. — Light which has been refracted from 
certain surfaces, or transmitted through certain substances, 
under certain special conditions, assumes new properties, 
and is no longer reflected, refracted, or transmitted a3 
before. This change in the action of light is called Po- 
larization, and a ray thus modified is said to be polarized. 

A ray of light which by any method has become polarized, seems to have 




Questions. — To what is this phenomenon due ? How may the diamond he distinguished 
from all other precious stones? What is polarized light ? What is the origin and ex- 
planation of this term ? 



PROPERTIES OF LIGHT. 121 

acquired a property of possessing sides. If the original ray be supposed to bo 
a cylindrical rod, polished or white all round, which is capable of being re- 
flected from a polished surface whatever part of its circumference may strike 
that surface, the polarized ray may be compared to a square-shaped rod with 
four flat sides, two of which (opposite), bright and polished, are capable of re- 
flection, while two, black or dull, are not. Now, the word " poles,'' in physi- 
cal science, is often used to denote the ends or sides of any body which havo 
acquired contrary properties, as the opposite ends of a magnet, which are 
called the positive and negative poles. By analogy, the ray of light whoso 
sides, situated at right angles with each other, were found to be endowed 
with opposite physical properties, was said to be polarized. The term is un- 
fortunate, but is too firmly engrafted upon science to be changed. 

The explanation of the change occasioned by polarization of light may be 
briefly stated as follows : — According to the undulatory theory, common light 
is assumed to be produced by vibrations of the ethereal particles in two planes 
at right angles to the progress of the wave ; there are perpendicular vibra- 
tions, and there are horizontal vibrations. Polarized light, on the contrary, 
is light occasioned by vibrations taking place in only one plane — the effect of 
whatever produces polarization being to suppress all the vibrations which 
take place in one plane at right angles to the other. Hence the different 
properties possessed by opposite sides or poles of the ray. 
Li^>Common light is converted into polarized light, for all practical purposes 
"P and for experiment, in three ways — 

First, — "When it is reflected from glass at an angle of incidence of fifty-sii 
degrees, forty-five minutes from the perpendicular. It is also polarized by 
reflection from almost any bright non-metallic surface, but the maximum po- 
larizing angle for each different surface is peculiar to itself. "When the re- 
flection from glass takes place at the exact angle of 56° 45', all the light is 
polarized, but when the angle of reflection deviates from this amount, some 
of the reflected light will remain unchanged, the quantity unpolarized being 
in proportion to the deviation. 

Secondly, — Light may be polarized by transmission through a bundle con- 
sisting of from sixteen to eighteen plates of thin glass or mica. 

Thirdly, — Light is polarized by passing through certain transparent crys- 
tals, especially those which possess the property of double refraction. 

199. Peculiarities of Polarized Ligh t'. — If a ray of light 
which has been polarized by reflection from a glass plate is caused to fall 
upon a second plate, it is not reflected as common light would be. If the 
plane of the second reflecting surface is so inclined to the first, that the. 
ray falls at an angle of 56°, the ray is not reflected at all, but vanishes; if, 
on the contrary, the plane of the second reflecting surface is parallel to the 
first, it is entirely reflected. It is also a peculiar property of polarized light, 



Questions. — In what three ways may light he polarized ? What peculiarities are mani- 
fested by light polarized by reflection from glass ? How is polarized light affected by 
certain transparent substances ? 

6 ' 




122 PRINCIPLES OF CHEMISTRY. 

that it will not pass through, certain substances which are transparent to com- 
mon light. This is shown in a remarkable manner by a mineral substance 
called tourmaline, the internal structure of which is such, that a ray of com- 
mon light which has passed through a thin plate of it, and thereby become 
polarized, can not pass through a second similar plate, if it is placed at right 
angles to the first. 

For example, in Fig. 56, if a ray of light be caused to pass through a thin 
plate of tourmaline, as c d, in the direction 
of the line a b, and be received upon a sec- 
ond plate, e f, placed symmetrically with the 
first, it passes through both without diffi- 
culty ; but if the second plate be turned a 
quarter round, as in the direction g h, the 
light is totally cut off. 

200. Discovery of Polarized Light , — The phenomenon of 
polarized light was discovered in 1808, by Malus, a young engineer officer of 
Paris. On one occasion, as he was viewing through a double refracting prism 
of Iceland spar the light of the sun reflected from a glass window in one of 
the French palaces, he observed some very peculiar effects. The window ac- 
cidentally stood open like a door on its hinges, at an angle of 56° and Malus 
noticed that the light reflected at this augle w T as endowed with properties 
which distinguish it from ordinary light. 

201. Practical Applications of Polarized Light . — The 
principles of polarized light have been applied to the determination of many 
practical results. Thus, it has been found that all reflected light, come from 
whence it may, acquires certain properties which enable us to distinguish it 
from direct light ; and the astronomer, in this way, is enabled to determine 
with infallible precision whether the light he is gazing on (and which may 
have required hundreds of years to pass from its source to the eye), is inhe- 
rent in the luminous body itself, or is derived from some other source by re- 
flection. 

It has been also ascertained by Arago that light proceeding from incandes- 
cent bodies, as red hot iron, glass, and liquids, under a certain angle, is po- 
larized light ; but that light proceeding, under the same circumstances, from 
an inflamed gaseous substance, such as is used in street illumination, is always 
in a natural state, or unpolarized. Applying these principles to the sun, ho 
discovered that the light-giving substance of this luminary was of the nature 
of a gas, and not a red hot solid or liquid body. 

When we transmit light, whether common or polarized, through a piece of 
well annealed glass, it suffers no change, and we see no structure in the glass 
different from what we would see if we looked through pure water. But if 

Questions.— Illustrate this in the case of tourmaline. When and how was polarized 
light discovered ? Vv'Tiat are some of the practical applications of polarized light ? What 
is the difference between light emitted from incandescent solids and inflamed gases? 
What inference has Arago made respecting the constitution of the sun ? What informa- 
tion does polarized light impart respecting the structure of bodies ? 



PROPERTIES OF LIGHT. 123 

we make heat pass through the glass, by placing the cdgo of the plate upon 
a heated iron, or if we either bend or compress the glass by mechanical force, 
its structure, or the mechanical condition of its particles, will be changed. If 
we now transmit common light through the glass thus changed, the change 
will not be visible ; but if we transmit polarized light through it, and allow 
that light to be reflected from a transparent body at an angle of about 56 c 
and in a plane at right angles to that in which the common light was reflected 
and polarized, the observer, looking through the glass, will see the most bril- 
liant colors, indicating the effects of the compressing or dilating forces, or of 
the contracting or expanding cause — the degree of compression or dilatation, 
cf expansion or contraction, being indicated by the colors displayed at par- 
ticular parts of the glass. In this way polarized light enables us to discover 
that certain portions of a body have been subjected to certain mechanical forces, 
the nature of which must be sought for in the circumstances under which tho 
body has been originally formed, or in which it has been subsequently placed. 
On this principle, many bodies which are quite transparent to the eye, and 
whioh upon examination appear to be perfectly uniform, or homogenous in 
structure, exhibit, under polarized light, the most exquisite organization.* 



* " Integumentary substances in particular form a brilliant and interesting class of ob- 
jects. A section of a horse's hoof has the effect of the richest Brussels' carpet, with a 
symmetrical pattern that might be copied by the loom. 

" The vegetable world has a less brilliant display to make, but is still replete with in- 
terest. Cuticles containing flint are often very beautiful ; that of the common marestail 
presents a remarkably neat shawl pattern in stripes. Very curious optical effects are pre- 
sented by the various starches. The starch called tous-les-mois, having the largest grains, 
is usually selected for exhibition. 

" Crystalline forms, however, afford the most striking exhibitions of the phenomena 
of polarized light. Salacine, a salt extracted from the bark of the willow, offers, when 
almost an imperceptible film, the appearance of a pavement consisting not merely of gold, 
but of lapis lazuli, ruby, emerald, and opal. Chlorate of potash strews the field of view 
with liberal handfuls of pyramidal jewels. Chromate of potash, which forms a bright 
yellow solution, presents a remarkable assemblage of club-shaped crystals, which have 
been compared to vast heaps of constables' 6taves. Oxalate of potash, like several other 
combinations of oxalic acid, is a salt of such variety and brilliancy, that its crystals, float- 
ing and glowing in a few drops of solution on the slide, look as if their form and color 
were the result of a Chinese imagination in its happiest moments. 

" Fancy yourself living in a region solely illuminated by Aurora borealis — imagine a 
country where every passing cloud throws a diverse-colored shadow of gorgeous hues 
across your path ; where the air breeds rainbows without the aid of a shower, and where 
the summer breeze breaks those rainbows into irregular lengths, fragments, and glitter- 
ing dust, scattering them broadcast over the land, like autumnal leaves swept by a gale 
from the forest, and you have an approximate, and by no means exaggerated idea of the 
effects of polarized light on substances capable of being affected by it. For, it is light en- 
dowed with extra delicacy, subtlety, and versatility. It renders visible minute details of 
structure in the most glaring colors ; it gauges crystalline films of infinitesimal thinness ■: 
it betrays to the student's search, otherwise inappreciable differences of density or elas- 
ticity in the various parts of tissues. Indeed, as a detector, polarized light is invaluable, 
acting the part of a spy under the most unexpected circumstances. It denounces as cot- 
ton what you believud to be silk ; it demonstrates disease where you supposed health. 
It adorns objects that arc vile and mean, whose destiny is only to be cast out — such as 
parings of nails, shavings of animals 1 hoofs, cuticle rubbed or peeled from the stems of 



124 PRINCIPLES OF CHEMISTRY. 

In a similar manner the chemist is able to determine, by the manner in 
which light is reflected or polarized by a erj'stallized body, whether it has 
been adulterated by the addition of foreign substances. Polarized light, also, 
in certain cases, affords the best means of arriving at a knowledge of the va- 
rieties and proportion of sugar in the juices of plants, and in complex sac- 
charine liquids. 

202. Magnetization of Ligh t. — Recent experiments made by 
Professor Faraday have proved that magnetism has the power of influencing 
a ray of light in its passage through transparent bodies. This fact is shown 
by the following experiment : — A ray of polarized light is passed through a 
piece of glass, or a crystal, or along the length of a tube filled with some trans- 
parent fluid, and the line of its path carefully observed ; if, when this is done, 
the solid or fluid body is brought under powerful magnetic influence, such as 
may be called into action by the circulation of an electric current around a 
bar of soft iron, it will be found that the polarized light is disturbed, and that 
it does not continue to pass through the medium along the same line. " As 
this effect is most strikingly shown in bodies of the greatest density and di- 
minishes in fluids, the particles of which are easily movable upon each other, 
and has not as yet been observed in any gaseous medium, the question has 
arisen, does magnetism act directly upon the ray of light, or only indirectly, 
by producing a molecular change in the body through which the ray is pass- 
ing ? In the present state of science no satisfactory reply can be given." — 
Robert Hunt. 

203. Decomposition of Light . — When a beam of light, S A, 
Fig. 57, from the sun is admitted into a dark room, by a small aperture in the 
window-shutter, and is intercepted in its passage by a wedge, or solid angle 
of glass called a prism, it is refracted, or bent from its course as it enters, 
and again as it issues from the glass. In place of forming a circular spot of 
white light on the floor of the apartment, as it would have done if allowed to 
proceed in its original direction, S K, it illuminates with several colors an 
oblong space, II, on the opposite wall, or on a white screen properly placed 
to receive it. This oblong colored image is called the prismatic, or solar 
spectrum. 

Newton, who first carefully investigated this remarkable fact, distinguished 
seven different colors, which gradually shade off one into the other in the 
following order, commencing at the upper part of the spectrum, viz., violet, 
indigo, blue, green, yellow, orange, and red. 

White light may, therefore, be regarded as the result 



plants, offscouring of our kitchens and store-rooms, sugar, acids, and salts — with the most 
magnificent, the most resplendent tints, such as are seen when the sun streams through 
the stained glass windows of a Norman cathedral." 

Questions. — Can polarized light be made available in determining the chemical char- 
acter of a substance ? What influence has magnetism on light ? What is meant by the 
decomposition of light ? What is the solar spectrum ? How are the colors of the spec- 
trum arranged ? How may white light be regarded ? 



PROPERTIES OF LIGHT. 



125 



of a mixture of rays o£ different colors, which are unequally 
acted upon by the prism — each color possessing its own 
peculiar refrangibility. 

Tims the red rays, which are the least refracted, or the least turned from 
their course by the prism, always occur at the bottom of the spectrum, while 
the violet, which is the most refracted, occurs at the top ; the remaining colors 
being arranged in the intermediate space in tbe order of their refrangibility. 




The seven different rays of light, when once separated and refracted by a 
prism, are not capable of being analysed by refraction again ; but if by means 
of a convex lens they are collected together and converged to a focus, they 
will form white light. 

204. Lines in the Solar Spectrum . — When the solar spec- 
trum is formed in the usual manner upon a white screen, it appears like a 
continuous band of colored light. By taking certain precautions, however, it 
may be seen that this luminous band is traversed in the direction of its 
breadth by numerous dark lines, varying in different parts in width and dis- 
tinctness ; or, in other words, there are interruptions in the spectrum where 
there is no light of any color. Those lines are independent of the refracting 
medium, and always occur in the same color and at corresponding points of 
the spectrum. 

The position of these dark spaces varies, however, with the source of light. 
"With a few exceptions, each of the fixed stars has a system of lines peculiar 
to it. The light proceeding from the fixed stars Sirius and Castor agree verf 
nearly in this respect, but differ from the light of the sun. The spectrum, 
however, which is formed from the light proceeding from the fixed star Pol- 



Questions Are the colored rays capable of further decomposition by refraction? 

What effect results from their union ? What lines are seen in the spectrum ? What dif- 
ferences have been observed in light emanating from different sources? 



126 



PRINCIPLES OF CHEMISTRY. 



lux is the same as that of the sun. Every artificial light, also, shows some 
peculiarity in this respect. 

Recent discoveries have given to these phenomena an entirely chemical 
character. It has been found that the white light of ordinary flames requires 
merely to be sent through a certain gaseous medium (such as nitrous acid 
vapor) to acquire more than a thousand dark lines in its spectrum ; and it 
has hence been inferred, that it is the presence of certain gases in the at- 
mosphere of the sun and of the fixed stars, which occasion the observed de- 
ficiencies in the spectra formed from their light. In this way points of re- 
semblance and difference may be traced between the constitution of our sun 
and the suns of other systems. 

In Fig. 58, No. 1 shows the principal dark lines of the pure solar spectrum ; 
No. 2, the alteration occasioned by passing solar fight through the vapor of 
bromine ; while No. 3 represents the very different result effected by the 
peroxyd of nitrogen. 

Fig. 58. 




205. Calorific and Chemical Elements of Solar Light . — 
Solar light, in addition to the luminous principle which 
produces the phenomena of color and is the cause of 
vision, contains two other principles, viz., heat and actin- 
ism, or the chemical principle. These principles are in- 
visible to the eye, and have only been discovered by their 
effects on other bodies. 

The constitution of the solar ray may be compared to a bundle of three 
sticks, one of which represents heat, another light, and a third the actinic 
principle. 

We know that these three principles exist in every ray of solar light, be- 
cause we are able to separate them in a great degree from each other. Thus, 
when we decompose a ray of solar light by means of a prism, and throw the 
spectrum upon a screen, the luminous, the calorific, and the chemical or ac- 
tinic radiations, will each be refracted, or bent out of their course in different 



Questions. — What discoveries have given to these lines a chemical character? What 
three principles are included in solar light ? How do we know of the existence of these 
principles ? How are they affected by the prism ? 



PROPERTIES OF LIGHT. 127 

degrees, and will consequently assume different positions upon the screen. 
In other words, the light of the sun refracted by the prism produces in reality 
three spectra, one visible and two invisible. 

The calorific, or heat radiations, will be refracted least, and their maximum 
point will be found but slightly thrown out of the right line which the solar 
ray would have traversed had it not been intercepted by the prism. The 
heat diminishes with much regularity on each side of this line. 

The luminous radiations are subject to a greater degree of refraction ; their 
point of maximum intensity being in the yellow ray, ljung considerably above 
the point of greatest heat. The light diminishes on each side of it, producing 
orange, red, and crimson colors below the maximum point, and green, blue, 
and violet above it. 

The radiations which produce chemical action are more refrangible than 
either the calorific or luminous radiations, and the maximum of chemical 
power is found at that point of the spectrum where light is feeble, and whero 
scarcely airy heat can be detected. 

The positions in the spectrum of the heat and actinic radiations, which are 
invisible to the eye, may be found by experiment. Thus, if we place a deli- 
cate thermometer in the different rays of the spectrum (§ 203, Fig. 57), it 
will be found that the indigo and violet rays scarcely affect it at all, while 
the yellow ray, which is the most luminous, is inferior in heating action to 
the red ray, which, yielding but little light, possesses the greatest amount 
of heat. If now the thermometer be carried a little below and just out of 
the red ray, into the darkened space, it will exhibit the greatest increase in 
temperature, thus proving the presence of a heating ray in solar light inde- 
pendent of the luminous ray. In a like manner, by substituting a chemically 
prepared surface, as a piece of photographic paper, for the thermometer, the 
presence of a chemical ray can be proved in the darkened space at the other 
end of the spectrum, and near to the blue and violet rays. 

206. Analysis of Heat . — The heat emanating from the sun or from 
a bright flame, consists of rays which differ from each other as much as the 
red, yellow, and blue rays do which constitute white light. Heat radiated 
from a body having a lower temperature than 800° F., is much less refrang- 
ible than red light ; but if the temperature of the radiating body be increased, 
it emits, in addition to the rays previously emitted, others of a higher refrang- 
ibility, until at last some few of its rays become as refrangible as the least 
refrangible rays of light. The body then appears of the same color as the 
least refrangible rays of light, and is said to be red hot. If it be heated more, 
it emits, in addition to the red, still more refrangible rays, viz., orange ; then 
(at a higher temperature) yellow rays are added, and so on, until when the 
body is white hot, it emits all the colors visible to us ; and in some instances 
(of very intense heat), even the invisible chemical rays, more refrangible than 
the violet, are emitted, though in less quantity than in the solar rays. 

Questions. — Is heat emanating from various sources uniform in character ? How d* 
the rays of heat differ in refrangibility ? 



128 PRINCIPLES OF CHEMISTRY. 

Thus light, in one sense, appears to he nothing more than visible heat, 
and heat invisible light — the constitution of the eye being such that it can 
perceive one and not the other, in the same way as the ear can appreciate 
vibrations of sound more rapid than sixteen per second, but not those which 
are less rapid. 

A series of interesting experiments made some years since by Melloni, 
show very conclusively that heat emanating from different sources differs in 
its nature, in the same manner as the light of a red body differs from that 
of a blue. He employed four sources of caloric, two of which were lumin- 
ous and two non-luminous, or obscure; namely, an oil- lamp without a glass, 
incandescent platinum, copper heated to 696° F., and a copper vessel filled 
with water at a temperature of 178° F. Rock-salt transmitted heat in the 
proportion of 92 rays out of every 100 from each of these sources ; but every 
other substance pervious to radiant heat, whether solid or liquid, transmitted 
more caloric from sources of high temperature than from such as were low. 
For instance, a clear and limpid mineral, the fluate of lime, transmitted in 
the proportion of 18 rays out of 100 from the lamp, 69 from the platinum, 
42 from the copper, and 33 from the hot water ; while transparent rock crys- 
tal transmitted 38 rays in 100 from the lamp, 28 from the platinum, 6 from 
the copper, and 9 from the hot water. Pure ice transmitted only in the 
proportion of 6 rays in the 100 from the lamp, and entirely excluded those 
from other sources. 

The discovery of the fact that heat proceeding from the sun or any other 
luminous body is susceptible of division into rays, differing in nature and in 
refrangibility, has furnished an explanation of many curious phenomena. 
Heat from very intense sources is more refrangible and passes more readily 
through most substances than heat of low intensity. Thus, the heat of the 
sun passes readily through glass, but the heat of a fire is almost entirely 
obstructed. Advantage has been taken of this fact by those who have oc- 
casion to inspect the progress of operations carried on in furnaces ; since they 
are able, by the use of a glass screen, to protect the face from the scorching 
rays which the glass absorbs, although it offers no impediment to the trans- 
mission of light. 

It is a well-known fact that snow which lies near the trunks of trees or 
other like substances, is melted much more rapidly than that exposed to the 
action of the direct rays of the sun. The reason of this is, that the heat of 
the sun, being heat of high intensity and high refrangibility, passes through 
the snow without experiencing a great degree of absorption ; but solar heat, 
which first falls upon the tree and is then radiated upon the snow, is thereby 
changed into heat of low refrangibility, and is readily absorbed instead of 
being transmitted. 

207. Action of the Chemical Rays . — The chemical principle 

Questions. — Describe the experiments of Melloni. What results have followed the dis- 
covery of the analysis of heat ? Why will glass transmit heat from the sun, and not from 
a fire ? How does the action of light on snow vary ? What is the character of the chem- 
ical principle of light? 






PROPERTIES OF LIGHT. 129 






of light is, without doubt, like the calorific principle, composed of rays of dif- 
ferent character, and of different refrangibihty. Recent experiments of Pro- 
fessor Stokes of England, seem to show that when the invisible rays which 
occupy in the spectrum a position beyond the violet, are caused to pass 
through a solution of quinine, they are changed in refrangibihty, and become 
visible — appearing as a sky-blue light at a point far beyond the usual lu- 
minous limit of the spectrum. This phenomenon has been termed the 
" degradation of light." 

The study of the chemical principle contained in the rays of solar light has 
rendered probable the curious fact, that no substance can be exposed to the 
sun's rays without undergoing a chemical change ; and from numerous ex- 
amples it would seem that the changes in the molecular condition of bodies 
which sunlight effects during the daytime, is made up during the hours of 
night, when the action is no longer influencing them. Thus darkness ap- 
pears to be essential to the healthy condition of all organized and unorgan- 
ized forms of matter. 

The process of forming Daguerreotype and other photo- 
graphic pictures, depends solely upon the actinic, or 
chemical influence of the solar ray. <\ 

The term " photography," signifying light drawing, which is the general 
name given to this art, is unfortunate and ill-chosen, for not only does light 
not exercise any influence in producing the pictures, but it tends to destroy 
them. 

That the luminous principle is not necessary for the success of the photo- 
graphic process, may be proved by the experiment of taking a daguerreotype 
in absolute darkness. This can be accomplished in the following manner : — 
A large prismatic spectrum is thrown upon a lens fitted into one side of a 
dark chamber ; and as the actinic power resides in great activity at a point 
beyond the violet ray, where there is no light, the only rays allowed to pass 
the lens into the chamber are those beyond the limit of coloration, and non- 
luminous ; these are directed upon any object, and from that object radiated 
upon a highly sensitive photographic surface. In this way a picture may be 
formed by radiations which produce no effect upon the eye. 

It has also been found that the yellow, the orange, and the red rays of 
light possess the power of retarding by their presence all chemical or pho- 
togenic action, in proportion to their predominance ; and if unaccompanied by 
other light, they arrest the effects of the chemical rays altogether. On the 
contrary, the violet, indigo, and blue rays of light favor chemical action. This 
is clearly exemplified in the following manner : — If an engraving be covered 
one half with a yellow glass, and placed in front of a camera for the pur- 

Questions. — What experiments have heen made hy Mr. Stokes '? What curious fact has 
the study of the chemical principle of light evolved ? Upon what does the production of 
photographic pictures depend ? What experiment shows that light is not necessary for the 
production of a photographic picture ? How do the different luminous rays of the solar 
beam affect the chemical principle ? What experiments and facts illustrate their rela- 
tive action ? 

6* 



130 PRINCIPLES OF CHEMISTRY. 

pose of representation on a daguerreotype plate, an accurate copy will be 
shortly obtained of the uncovered portion, while the yellow screen • entirely 
prevents the plate from receiving an impression of the rest. But if the en- 
graving be covered, one half with blue and the other half with yellow glass, 
while it will bo distinctly discernible to the eye through the latter and not 
at all through the former, the camera will faithfully copy the portion which 
is invisible, but wholly neglect the other. Again, in a room illuminated solely 
through red, or orange glass, in which light may fall with dazzling luster, no 
photographic operations can be conducted ; while if blue glass be substi- 
tuted, the change, while it will dim the effulgence, will enable the photo- 
grapher to exercise his art with success. In the same way, during certain 
states of the atmosphere, there may be an abundance of illuminating, but 
very few photogenic rays. 

208. Influence of Light on Vegetation . — There are many 
reasons for supposing that each of the three principles, light, heat, and actin- 
ism, included in the solar ray, exercise a distinct and peculiar influence upon 
vegetation. Thus the luminous principle contrcls the growth and coloration 
of plants, the calorific principle their ripening and fructification, and the chem- 
ical principle the germination of seeds. Seeds which ordinarily require ten 
or twelve days for germination, will germinate under a blue glass in two or 
three. The reason of this is, that the blue glass permits the chemical prin- 
ciple of light to pass freely, but excludes, in a great measure, the heat and 
the light. On the contrary, it is nearly impossible to make seeds germinate 
under a yellow glass, because it excludes nearly all the chemical influence 
of the solar ray. 

Further consideration of the chemical effects of light will be postponed 
until after the chemical properties of the elementary bodies have been de- 
scribed. 



X 



CHAPTER IV. 



ELECTRICITY. 



209. Electricity is a subtile agency or force, without 
weight or form, that appears to be diffused through all 
nature, existing in all substances without affecting their 
volume or their temperature, or giving any indication of 
its presence when in a latent, or ordinary state. When, 
however, it is liberated from this repose, it is capable of 

Questions. — What influence do the three principles of the solar ray exert on vegetation ? 
What is electricity ? 



ELECTRICITY. 131 

producing the most sudden and destructive effects, or of 
exerting powerful influences by a quiet and long-continued 
action. 

We are unable to say whether electricity is a material substance, a property 
of matter, or the vibration of an ether. The general opinion at the present 
day, however, is, that electricity, like light and heat, is the result of some 
modification, or vibration of that subtile ethereal medium which pervades all 
space, and which is capable of moving with various degrees of facility through 
the pores of even the densest substances. 

The language which is almost universally adopted in describing electrical 
phenomena, is based upon the supposition that electricity is a form, or kind 
of matter, since by the use of this hypothesis, the leading facts of the science 
may be clearly and simply set forth. 

210, Electricity and Chemical Action.— The relation 
which exists between the force of electricity and the opera- 
tions of chemical affinity is most intimate ; and according 
to some authorities electricity and chemical affinity are 
merely different manifestations of the same agent. 

211. Excitation of Electricity,— Electricity may be ex- 
cited, or called into activity by mechanical action, by 
chemical action, by heat, and by magnetic influence. 

Why the means above enumerated should develop electricity, or excite it 
from a neutral condition, is a matter at present wholly inexplicable. 

212; Two Conditions of Electricity.— Electricity in the 
act of becoming free, as when excited by friction, or when 
evolved from a galvanic battery, appears to separate into 
two forces, or, as it is generally termed, into two kinds of 
electricity. These two forces are identical in their nature 
and equal in power, but opposite and contrary in their ac- 
tion. When they meet, they do not unite to form a 
double electrical force, but they mutually neutralize and 
destroy the power of each other. 

The existence and action of these two forces, or kinds of electricity, may be 
demonstrated by the following simple experiment : — If we take a dry glass 
rod, rub it well with silk, and present it to a light pith baU, or feather, P, 

Questions. —What do we know concerning the real nature of this agent ? What is the 
relation between electricity and chemical action ? How may electricity he excited ? In 
what manner does electricity, on being set free, display itself? What is the character of 
the two forces, or kinds of electricity ? How may the existence and action of the two 
kinds of electricity be demonstrated? 



132 



PRINCIPLES OF CHEMISTRY 



Fig. 59. 




Fig. 60. 




Fig. 59, suspended from a support by a silk thread, the ball or feather will be 
attracted toward the glass, as seen at G. After it has adhered to it a moment, 
it will fly off, or be repelled, as P' from G-'. The 
same thing will also happen if sealing-wax be 
rubbed with dry flannel, and a like experiment 
made. 

If, however, the action of the glass and the 
wax be compared together, a remarkable differ- 
ence between the two will immediately manifest 
itself, for when the glass repels the ball the seal- 
ing-wax will attract it most strongly, and when 
the wax repels, the glass attracts in like manner; 
so that if we suspend a light pith ball, or feather, by a silk thread, as in Fig. 
60, and present a stick of excited sealing-wax, S, on one side, 
and a tube of excited glass. G, on the other, the ball will 
commence vibrating like a pendulum from one to the other, 
being alternately attracted and repelled by each, the one at- 
tracting when the other repels. We therefore conclude that 
the electricities excited in the glass and wax are different. 

la order to distinguish the two opposite 
forces or conditions of electricity from each 
other, that force which is obtained from the glass has "been 
termed vitreous, or positive electricity ; and that from the 
wax, resinous, or negative electricity. 

While the terms vitreous and resinous are now rarely used, those of posi- 
tive and negative are somewhat unfortunate, since they almost unavoidably 
convey to the learner the impression that the one force is stronger or more 
potent than the other, whereas the negative electricity has as positive an ex- 
istence and as substantial power as the opposite electricity. 

Electricity may be excited in all bodies. There are no exceptions to this 
fact, but electricity is developed in some bodies with great ease, and mothers 
with great difficulty. In no case, however, can electricity of one kind be 
excited without setting free a corresponding amount of electricity of the 
other kind ; hence, when electricity is excited by friction, the rubber always 
exhibits the one, and the body rubbed, the other. 

213. Fundamental Law of Electricity.— The funda- 
mental law which governs the relation of the two forces 
of electricity to each other may be expressed as follows : 

Like electricities repel each other, unlike electricities 
attract each other. 



Qttestions. — By what names do we distinguish the two forces, or kinds of electricity? 
"Why is the use of the terms positive and negative unfortunate ? Can one electricity he 
developed independently of the other '? What is the great fundamental law of electricity ? 



ELECTRICITY. 13& 

Thus, if two substances are charged with positive electricity, they repel 
each other; two substances charged with negative electricity also repel each 
other ; but if one is charged with positive and the other with negative elec* 
tricity, they attract each other. 

The attraction which the two opposite electricities have for each other is 
revy great, and their tendency is, therefore, constantly to combine together. 
From such combination latent, or quiescent electricity results. 

214. Electrified and Non-Electrified Bodies.— When a 
body holds its own natural quantity of electricity undis- 
turbed, it is said, to be non-electrified. 

When an electrified body touches one that is non-elec- 
trified, the electricity contained in the former is trans- 
ferred in part to the latter. 

Thus, on touching the end of a suspended silk thread with a piece of ex- 
cited wax or glass, electricity will pass from the wax or glass into the silk, 
and render it electrified ; and the silk will exhibit the effects of the electricity 
imparted to it, by moving toward any object that may be placed near it. -J 

215. Conductors and Non-Conductors. — Bodies differ 
greatly in the freedom with which they allow electricity 
to pass over or through them. Those substances which 
facilitate its passage are called conductors ; those that re- 
tard, or almost prevent it, are called non-conductors. 

No substance can entirely prevent the passage of electricity, nor is there 
any which does not oppose some resistance to its passage. 

Of all bodies, the metals are the most perfect conductors of electricity ; 
charcoal, the earth, water, moist air, most liquids, except oils, and the human 
body, are also good conductors of electricity. 

Gum shellac and gutta percha are the most perfect non-conductors of elec- 
tricity; sulphur, sealing-wax, resin, and all resinous bodies, glass, silk, 
feathers, hair, dry wool, dry air, and baked wood, are also non-conductors. 

Electricity always passes by preference over the best conductors. 

216. Insulation. — When a conductor of electricity is 
surrounded on all sides by non-conducting substances, it 
is said to be insulated ; and the non-conducting substances 
which surround it are called insulators. 

"When a conducting body is insulated, it retains upon its surface the elec- 
tricity communicated to it, and in this condition it is said to be charged with 
electricity. 

Questions. — Illustrate it. When is a body said to be electrified, and -when non-electri- 
fied? What are conductors and non-conductors of eleetricity? What substances are 
good conductors ? What are bad conductors ? When is a conductor said to be insulated ? 
When charged ? 



134 PKINCIPLES OF CHEMISTRY. 

217. Velocity of Electricity. — The velocity with which 
the influence of electricity passes through good conduc- 
tors is so great, that the most rapid motion produced by 
art appears to be actual rest when compared to it. Some 
authorities have estimated that frictional electricity will 
pass through copper wire at the rate of 288 ; 000 miles in 
a second of time — a velocity greater than that of light. 
The results obtained, however, by the United States Coast 
Survey, with galvanic electricity and iron wire, show a 
velocity of from 15,000 to 20,000 miles per second. 

The terms " electric fluid" and " electric current," which are frequently em- 
ployed in describing electrical phenomena, are calculated to mislead the stu- 
dent into the supposition that electricity is known to be a fluid, and that it 
flows in a rapid stream along a conductor. Such terms, it should be un- 
derstood, are founded merely on an assumed analogy between the electric 
force and a fluid substance. The nature of that force, however, is unknown, 
and whether its transmission be in the form of a current, or by vibrations, is 
undetermined.* v 

218. Galvanic, or Voltaic Electricity.— Electricity ex- 
cited or produced by the chemical action of two or more 
dissimilar substances upon each other, is termed Galvanic, 
or Voltaic Electricity, and the department of physical 
science which treats of this form of electrical disturbance 
ij called Galvanism. 

The most simple method of illustrating the production of galvanic electricity 
is by placing a piece of silver (as a coin) on the tongue, and a piece of zinc 
underneath. So long as the two metals are kept asunder no effect will be 
noticed, but when their ends are brought together a distinct thrill will pass 
through the tongue, a metallic taste will diffuse itself, and, if the eyes are 
closed, a sensation of light will be evident at the same moment. 

This result is owing to a chemical action which is developed the moment 



* In a discussion which took place some years since at a meeting of the British Associa- 
tion for the Advancement of Science, respecting the nature of electricity, Professor Fara- 
day expressed his opinion as follows :-^" There was a time when I thought I knew some- 
thing about the matter ; but the longer I live, and the more carefully I study the subject' 
the more convinced I am of my total ignorance of the nature of electricity." 

" After such an avowal as this," says Mr. Bakewell, " from the most eminent electrician 
of the age, it'is almost useless to say that any terms which seem to designate the form of 
electricity are merely to be considered as convenient conventional expressions." 

Questions. — What is the velocity of electricity? What is understood by the use of the 
word current, as applied to electricity ? What is galvanic, or voltaic electricity ? What 
its the most simple method of illustrating its production ? To what is this result owing ? 



ELECTRICITY 



135 



the two metals touch each other. The saliva of the tongue acts chemically 
upon, or oxydizes a portion of the zinc, which excites electricity, for no chem- 
ical action ever takes place without producing electricity. Upon bringing 
the ends of the two metals together, a slight current passes from one to the 
other. 

219. Discovery of Galvanic Electricity. — The produc- 
tion of electricity by the chemical action of two metals 
when brought in contact, was first noticed by Galvani, 
a professor of anatomy at Bologna, Italy, in 1790. 

His attention was directed to the subject in the following manner : — Hav- 
ing occasion to dissect several frogs, he hung up their hind legs on some cop- 
per hooks, until he might find it necessary to use them for illustration. In 
this manner he happened to suspend a number of the copper hooks on an 
iron balcony, when, to his great astonishment, the limbs were thrown into 
violent convulsions. On investigating the phenomenon, he found that the 
mere contact of dissimilar metals with the moist surfaces of the muscles and 
nerves, was all that was necessary to produce the convulsions. 

Fig. 61. 




This singular action of electricity, first noticed by Galvani, may be experi- 
mentally exhibited without difficulty. Fig. 61 represents the extremities of 
a frog, with the upper part dissected in such a way as to exhibit the nerves 

Questions. — When and how was galvanic electricity discovered ? How may the phe- 
nomenon first noticed by Galvani he experimentally repeated ? 



136 



PRINCIPLES OF CHEMISTRY. 



of the legs, and a portion of the spinal marrow. If we now take two thin 
pieces of copper and zinc, C Z, and place one under the nerves, and the other 
in contact with the muscles of the leg, we shall find that so long as the two 
pieces of metal are separated, so long will the limbs remain motionless- but 
by making a connection, instantly the whole lower extremities will be thrown 
into violent convulsions, quivering and stretching themselves in a manner 
too singular to describe. If the wire is kept closely in contact, these phen- 
omena are of momentary duration, but are renewed every time the contact is 
made and -broken. 

Galvani attributed these movements of the muscles to a kind of nervous 
fluid pervading the animal system, similar to the electric fluid, which passed 
from the nerves to the muscles, as soon as the two were brought in commu- 
nication with each other, by means of the metallic connection. He therefore 
called the supposed fluid animal electricity. 

220. The Voltaic Pile .—The experiments of Galvani were re- 
peated by Volta, an eminent Italian philosopher, who found that no electrical 
or nervous excitement took place unless a communication between the muscles 
and the nerves was made by two different metals, as copper and iron or 
copper and zinc. He also observed that all the effects noticed could be pro- 
duced in a much higher degree by using a number of pieces of different 
metals and a fluid, or a substance moistened with 
a fluid. He accordingly arranged a series of coo- 
per and zinc plates in a pile with cloths wet in a 
saline or acid liquid between them, as is repre- 
sented in Fig. 62. The series commenced with a 
zinc plate, upon which was placed a copper plate 
of the same size, and on that a circular piece of 
cloth previously soaked in water slightly acidu- 
lated. On the cloth was laid another plate of 
zinc, then copper, and again cloth, and so on in 
succession, until a pile of fifty series of alternate 
metal plates and moistened cloths was formed, the 
terminal plate of the series at one end being cop- 
per and at the other end zinc. Such an apparatus 
received the name of a " Voltaic Pile,'" and its ef- 
fects were soon seen to be of an electrical char- 
acter. 

For instance, if the two ends or terminal plates of the pile were touched, 
one with each hand previously moistened, a sensation similar to that of an 
electric shock was experienced. If the two ends were connected by means 
of metallic Avires, sparks could be obtained, shocks communicated, and many 
other electrical effects produced. 




firSnSz 



Questions.— To what did Galvani attribute the results by him noticed ? What conclu- 
sion was arrived at by Volta? What discovery did Volta make? Describe the voltaic 
pile. 






ELECTRICITY. 137 

221. Results of Galvani's and Volta's Discoveries.— 

Such is an outline of one of the greatest and most remarkable discoveries of 
modern times — a discovery which illustrates in a striking manner the im- 
portance of cultivating correct habits of observation, and of rightly estimating 
the relations which exist between a cause and its effect. The attention be- 
stowed by Galvani on the simple circumstance of the twitching of a frog's 
legs in 1*790, led to the discovery of the voltaic pile in 1800, a modification of 
which constitutes the present galvanic battery. Since the last named period 
the progress of discovery has been most rapid, embracing the whole science 
of electro-magnetism, electro -metallurgy, the application of electricity to 
chemical analysis, to the production of intense heat and light, to the recording 
of time, to the determination of longitudes, and finally, to the almost instan- 
taneous communication of intelligence by means of the telegraph. 

Volta considered that electricity was produced by simple contact of dis- 
similar metals, positive electricity being evolved from the one, and negative 
from the other. It is now generally believed that chemical action, taking 
place between the surfaces in contact, is the sole cause of exciting and con- 
tinuing the electric currents. 

222. Fundamental Principle of Galvanic Electricity. — 

The fundamental principle which forms the basis of the 
science of galvanic electricity is as follows : 

Any two metals, or more generally, any two different 
bodies which are conductors of electricity, when placed in 
contact, develop electricity by chemical action — positive 
electricity flowing from the body which is acted upon most 
powerfully, and negative electricity from the other. 

223. Electro-positive and Negative Elements, — In gen- 
eral, that substance which is acted upon most easily is 
termed the electro-positive element ; and the other the 
electro-negative element. 

The electrical force or power generated in this way is 
called the electro-motive force. 

Different bodies placed in contact manifest different 
electro-motive forces, or develop different quantities of 
electricity. 

Bodies capable of developing electricity by contact may be arranged in a 



Questions. — What have been the results of Galvani's and V lta's discoveries ? What 
did Volta suppose to be the origin of the electricity of the pile ? What is now believed oa 
this subject? What is the fundamental principle of galvanic electricity? What are elec- 
tro-positive and electro-negative elements? What is understood by the term electro- 
motive force ? How may bodies capable of exciting electro-motive forco be classed ? 



13S 



PRINCIPLES OF CHEMISTRY 



Fig. 63. 



series in such a manner that any one placed in contact with another holding 
a lower place in the series, will receive the positive fluid, and the lower one 
the negative fluid ; and the more remote they stand from each other in the 
order of the series, the more decidedly will the electricity be developed by 
their contact. 

The most common substances used for exciting galvanic electricity may be 
arranged in such a series as follows : — zinc, lead, tin, antimony, iron, brass, 
copper, silver, gold, platinum, black lead or graphite, and charcoal. 

Thus, zinc and lead, when brought in contact, will produce electricity, but 
it will be much less active than that produced by the union of zinc and iron, 
or the same metal and copper, and the last less active than zinc and platinum 
or zinc and charcoal. 

224. Zamboni's Pile . — According to the principles above explained, 
a perfectly dry pile, known from its inventor as Zamboni's pile, may be con- 
structed of sheets of gilded paper and sheet zinc. If 
several thousand of these bo packed together in a 
glass tube, so that their similar metallic faces shall all 
look the same way, and be pressed tightly together 
at each end by metallic plates, it will be found that 
one extremity of the pile is positive and the other 
negative. Such a series will last more than twenty 
years, but it requires as many as 10,000 pairs to af- 
ford sparks visible in daylight. 

Fig. 63 represents a pair of these piles,, so arranged 
as to produce what has been called a perpetual mo- 
tion. Two piles, P N, are placed in such a position 
that the positive extremity of one pile is opposite and 
near to the negative extremity of the other. Be- 
tween them a light pendulum is placed, vibrating on 
an axis and insulated on a glass pillar. This pen- 
dulum is alternately attracted to one and then to the 
other, and thus rings two little bells connected with 
the positive and negative poles. 
In a similar manner, voltaic piles have been constructed entirely of vege- 
table substances, without resorting to the use of any metal, by placing discs 
of beet-root and walnut-wood in contact. "With such a pile, and a leaf of 
grass as a conductor, convulsions in the muscles of a dead frog are said to 
have been produced. Other experimentalists have formed voltaic piles wholly 
of animal substances. 

225. Practical Production of Galvanic Electricity. — In 
the production of galvanic electricity for practical pur- 
poses, it is necessary to have a combination of three dif- 




Questioxs. — Describe the dry, or Zamboni's pile. May a voltaic pile be produced en- 
tirely of vegetable or animal substances ? "What arrangement is necessary for the practi- 
cal production of galvanic electricity 1 



ELECTRICITY 



139 



ferent conductors, or elements, one of which must be 
solid and one fluid, while the third may he either solid or 
fluid. 

The process usually adopted is to place between two plates of different 
kinds of metal a liquid capable of exciting some chemical action on one of the 
plates, while it has no action, or a different action upon the other. A com- 
munication is the a formed between the two plates. ^ 

226. Galvanic Circuit. — When two metals capable of 
exciting electricity are so arranged and connected that the 
positive and negative electricities can meet and flow in 
opposite directions, they are said to form a galvanic cir- 
cuit, or circle. Such an arrangement is very generally 
termed, also, a simple galvanic battery. 

A very simple, and at the same time 
an active galvanic circuit may be formed 
by an arrangement as represented in 
Tig. G4. C and Z are thin plates of 
copper and zinc immersed in a glass 
vessel containing a very weak solution 
of sulphuric acid and water. So long 
as the two metals do not touch each 
other, there will be but slight chemical 
action, and consequently little or no 
electricity evolved ; but on bringing the 
two end3 of the metal strips together, or 
by causing metallic contact by a con- 
nection of wires, X and "W, a galvanic 
circuit will be formed, positive elec- 
tricity passing from the zinc through the liquid to the copper, and from tho 
copper along the conducting wires to the zinc, as indicated by the arrows in 
the figure. A current of negative electricity at the same time traverses the 
circuit also, from the copper to the zinc, in an opposite direction. 

22*7. Theory of a Simple Circuit — In the formation of a gal- 
vanic circuit, by the employment of two metals and a liquid, the chemical ac- 
tion which gives rise to the electricity takes place through a decomposition 
of the liquid. 

"When a plate of zinc and one of copper are immersed in water acidulated with 
sulphuric acid, the elements of the water, oxygen and hydrogen, are separated 
from each other, in consequence of the greater attraction which the oxygen 
has for the zinc. The oxygen, therefore, unites with the zinc, and by so doing 




Questions. — What is a galvanic circuit, or simple galvanic battery? Deseribe the con- 
struction of such a circuit. What is the origin of the electricity evolved in a circuit 
composed of two metals and one liquid ? Describe the theoretical action of such a circuit ? 



140 PEINCIPLES OF CHEMISTRY. 

excites, or develops electricity in the metal. Eut as one kind of electricity 
can not be evolved without bringing an equal quantity of the other into ac- 
tivity, the act which develops negative electricity in the metal, instantaneously 
dovelops positive electricity in the liquid. It would naturally be supposed, 
that as the two opposite electricities have a strong attraction for each other, 
t'.iat they would again unite, and restore the equilibrium ; such, however, 
f/om some unexplained reason, is not the case ; but the electrical and chem- 
ical changes are so connected, that unless the equilibrium is restored, the 
action between the metal and the liquid will stop as soon as a certain quan- 
tity of electricity has accumulated. If, under these cireumstaftces, the copper 
plato which is immersed in the liquid, but not acted upon by it, be brought 
in contact with the zinc, it will serve as a conductor, and will convey the 
positive electricity accumulated in the liquid to the zinc, restore the equili- 
brium of the two electricities, and cause the action between the liquid and the 
zinc to recommence. "With the commencement of the flow of positive elec- 
tricity from the liquid to the copper, and from the copper to the zinc, a cur- 
rent of negative electricity will tend to flow in the opposite direction, or from 
the zinc to the copper, and from the copper to the liquid.* 

228. Direction of the Current.— In all cases, the direc- 
tion of the current is dependent on the direction of the 
chemical action. 

The positive electricity always sets out from the metal most acted upon by 
the exciting liquid, which may be, therefore, called the generating or posi- 
tive plate. It traverses the liquid toward the less affected metal, which forms 
the negative, or conducting plate, and from this the force is transferred to the 
wire, or other conducting medium, between the two plates ; thence it passes 
back again to the generating plate. In this way the circuit is completed, and 
unless this circulation can take place, all the phenomena of galvanic action 
will be suspended. 

The electrical condition of the plates of copper and zinc as above described, 
it should be understood, applies only to those portions of the two metals 
which are immersod in the liquid. Those parts which are out of the liquid, 
and in the air, are in an exactly opposite condition. Thus the end of the zinc 
in the acid is -{-, or positive, while that in the air is — , or negative. The 
electrical state of the two ends of the copper is exactly the reverse. 

If, in the arrangement above described, some liquid which acts upon the 
copper in preference to the zinc, as ammonia, had been used, the electrical 



* In every voltaic current it is assumed that a quantity of negative electricity, equal to 
that of the positive set in motion, is proceeding along the conducting medium in a direc- 
tion opposite to that in which the positive electricity is traveling ; but in order to avoid 
confusion, whenever the direction of the current is mentioned, the direction of the posi- 
tive electricity is alone referred to. 



Questions, — What influences the direction of the current ? What determines the elec- 
trical condition of the immersed metals ? 



ELECTRICITY. 141 

condition of the two metals, and the direction of the flow of electricity, would 
have been reversed. 

Although two metal plates are usually employed in a simple galvanic 
circuit, only one of them is active in the excitement of electricity, the other 
plate serving merely as a conductor to collect the force generated. A metal 
plate is generally used for this purpose, because metals conduct electricity 
much better than other substances exposing an equal surface to the fluids 
in which they are immersed ; but other conductors may be used, and when 
a proportionately larger surface is exposed to compensate for inferior con- 
ducting power, they answer as well, and in some instances better, than metal 
plates. Thus charcoal is very often employed in the place of copper, and a 
very hard material obtained from the interior of gas retorts, "gas- carbon," 
is considered one of the best conductors. 

Two metals are not absolutely essential to the formation of a simple gal- 
vanic current. A current may be obtained from one metal aDd two liquids, 
provided the liquids are such that a stronger chemical action takes place on 
one side of the metal plate than on the other. 

229. Poles of a Galvanic Battery. — The two metals 
forming the elements of the battery are generally connected 
by copper wires ; the ends of these wires, or the terminal 
points of any other connecting medium used, are called 
the poles of the battery. 

Thus, when zinc and copper plates are used, the end of the wire conveying 
positive electricity from the copper would bo the positive pole, and the end of 
the wire conveying negative electricity from the zinc plate would be the 
negative pole. Faraday describes the poles of the battery as the doors by 
which electricity enters into or passes out of the substance suffering decom- 
position, and in accordance with this view he has given to the positive polo 
the name of anode, or ascending way, and to the negative pole the name of 
cathode, or descending way. 

The manifestations of electricity will be most appa- 
rent at that point of the circuit where the two currents 
of positive and negative electricity meet. 

When the two wires connecting the metal plates of a battery are brought 
in contact, the galvanic circuit is said to be closed. Ko sign of electrical ex- 
citement is then visible ; the action, nevertheless, continues. The opposite 
electricities collected at the poles, in particular, neutralize each other perfectly 
on meeting ; every trace of electricity must therefore vanish if a fresh quan- 
tity were not continually produced by the continuance of the chemical action. 

Questions. — What is the necessity of two metals in a galvanic circuit ? Under what 
circumstances can some other substance be substituted in place of the copper ? What 
are the poles of a galvanic battery ? What is tbe meaning of the terms anode and 
cathode? At what point of a galvanic circuit will the manifestation of electricity be most 
apparent ? When is the galvanic circuit said to be closed ? 



142 



PRINCIPLES OF CHEMISTRY, 



230. Compound Circuit. — The electricity developed by 
a simple galvanic circuit, whether it be composed of two 
metals and a liquid, or any other combination, is exceed- 
ingly feeble. Its power can, however, be increased to any 
extent by a repetition of the simple combinations. 

The discovery of this fact was first made by Volta, and applied by him hi 
the voltaic pile before described. 



Fig. 65 




Fig. 65 represents, in its simplest form, the construction of a compound 
galvanic circuit, by the union of a number of simple circuits. Each glass 
contains one zinc and one copper plate, which are not immediately connected 
together as in a simple circuit ; but every zinc plate is connected with tho 
copper plate of the preceding glass by a copper wire or band. In the figure, 
the copper plate and the direction of the positive current is represented by the 
sign -{-, and the zinc plate and the negative current by the sign — . 

In a compound galvanic circuit, like the one represented in Fig. 65, the 
positive electricity which the fluid in the first vessel acquires from the plate 
of zinc exposed to its action, is taken up by the copper plate and transferred 
to the second zinc plate in the second vessel, by means of its metallic con- 
nection. This transmits it, together with what itself generates, to the liquid 
of the second vessel. From this the double force is passed to the next cop- 
per, and by it to the third zinc, which it touches, and so on, every succeeding 
alternation being productive of a further increase in the quantity of the elec- 
tricity developed. A current of negative electricity may in like manner be 
supposed to flow in an opposite direction, its quantity augmenting with each 
successive pair of plates. This action, however, would stop unless an outlet 
were given to tho accumulated electricity by establishing a communication 
between the positive and negative poles of the battery, by means of wires 
attached to the extreme plate at each end. When these are brought into 
contact, the galvanic circuit is completed, and the electricities meet and neu- 
tralize each other, producing the various electrical phenomena. The electric 
current continues to flow uninterruptedly in the circuit so long as the chem- 
ical action lasts. 



Questions. — What is the electrical power of a simple circuit "? II ow may it be increased ? 
Describe the construction of a compound circuit? In what manner dois it accumulate 
electricity ? 



ELECTRICITY. 



143 



Fig. 66. 




The simple and compound voltaic circuits in practical use, which in ordi- 
nary language are both designated as galvanic batteries, differ considerably 
in form and efficiency. The general principle of construction in all, however, 
is the same as that of the original voltaic pile. ~A -, 

231. The Trough Battery . — One of t£e earliest forms contrived 
is known as the Trough Battery, represented in Fig. 66. It consists of a 
trough of wood divided into Water- 
tight cells, or partitions, each cell 
being arranged to receive a pair of 
zinc and copper plates. The plates 
are attached to a bar of wood, and 
connected with one another by me- 
tallic wires, in such a way that every 
copper plate is connected with the 
zinc plate of the next cell. The bat- 
tery is excited by means of dilute 
sulphuric acid poured into the cells, 
and the current of electricity is di- 
rected by wires soldered to the ex- 
treme plates. "When the battery is not in use the plates may be raised 
from the trough by means of the wooden bar. 

The battery by which Sir Humphrey Davy effected his splendid chemical 
discoveries was of this form, and consisted of two thousand double plates of 
copper and zinc, each plato having a surface of thirty-two square inches. 
Now, however, by improved arrangements, we can produce with ten or 
twenty pairs of plates, effects every way superior. 

232. Smee's Battery . — The most easily managed 
form of galvanic battery at present used is that invented by 
Mr. Smee, and known as Smee's battery. (See Fig. 67.) It 
consists of a plate of silver coated with platinum, suspended 
between two plates of zinc, z z, the surfaces of which last have 
been coated with mercury, or amalgamated, as it is called. 
The three are attached to a wooden bar, which serves to sup- 
port the whole in a tumbler, G, partially filled with a weak 
solution of sulphuric acid and water. The wires, or poles for 
directing the current of electricity are connected with the zinc 
and platinum plates by small screw-cups, S and A. 

233. Amalgamation of Zinc . — The introduction of the process 
of amalgamating, or coating the zinc plates of a galvanic circuit with mer- 
cury, constituted an improvement of great value. In the original form of 
the galvanic battery, constructed of copper and ordinary metallic zinc, the 
waste of the latter metal by the action of the exciting acid upon it was very 



Fig. 67, 



QTrEBTTOMB. — Describe the trough battery. What is the construction of Smee's battery ? 
"What is understood by the amalgamation of tho zinc? "What benefit results from this 
operation? 



144 



PRINCIPLES OF CHEMISTRY, 



great ; but by using- amalgamated zinc this waste is diminished in an extra- 
ordinary degree, without at the same time diminishing the production of 
electricity. All improved batteries are, therefore, constructed with amalga- 
mated zinc. 

234. Sulphate of Copper Battery ,— Another form of battery, 
called the sulphate of copper battery, from the fact that a solution of sul- 
phate of copper (blue vitriol) is used as the exciting liquid, is represented by 
Fig. 68. It consists of two concentric cylinders of cop- 
per, C, tightly soldered to a copper bottom, and a zinc 
cylinder, Z, fitting in between them. Two screw-cups 
for holding the connecting wires are attached, one to 
the outer copper cylinder, and the other to the zinc. 

The principal imperfection of the galvanic battery is 
the want of uniformity in its action. In all the various 
forms, the strength of the electric current excited con- 
stantly decreases from the moment the battery action 
commences. In the sulphate of copper battery, espe- 
cially, the power is reduced in a comparately short time 
to almost nothing. This is chiefly owing to the circum- 
stance, that the metallic plates soon become coated with the products of tho 
chemical decomposition, the result of the chemical action whereby the elec- 
tricity is developed. 

This difficulty is obviated in a great degree by the use of a diaphragm, or 
a porous and permeable partition between the two metallic plates, which al- 
lows a free contact of the liquid on both sides within its pores, but prevents 
the solid products of the chemical action from passing from one metallic plate 
to the other. Bladder, leather, clay, porce- 
lain, cloth, etc., have been used for this pur- 




FiG. 69. 




235. Daniel's Constant Battery, 

constructed according to the above described 
principle, and represented by Fig. 69, main- 
tains an effective galvanic action longer than 
any other. The outer case, C, consists of a 
cell, or cylinder of copper, which is so con- 
structed as to retain liquids, and is filled with a 
solution of sulphate of copper, B, acidulated 
with one eighth of its .bulk of sulphuric acid. 
The solution is kept saturated ' with the salt 
by means of crystals of sulphate of copper, 
D, which rest upon the perforated shelf, F. 
In the center of the cell is placed a tube of porous earthen- ware, E, filled with 



Questions. — Describe the sulphate of copper battery. What is the principal imperfec- 
ion of the galvanic battery ? How is it obviated ? What is the construction of Daniel's 
battery ? 



ELECTRICITY. 



145 



an acid solution, A, which consists of one part of sulphuric acid diluted with 
seven parts of water. A rod of zinc, Z, is placed in this tube. On making a 
metallic communication between the zinc rod and the copper cell, a voltaic 
current is established. 

236. Grove's Battery . — One of the most efficient batteries is that 
known as Grove's battery, from its inventor, and is the form generally used 
for telegraphing, and other purposes in which powerful galvanic action is re- 
quired. It is constructed upon the same general principle as Daniel's battery, 
and consists of a plain glass tumbler, in which is placed a cylinder of amal- 
gamated zinc, with an opening on one side to allow a free circulation of the 
liquid. Within this cylinder is placed a porous cup, or cell of earthenware, 
in which is suspended a strip of platinum fastened to the end of a zinc arm 
projecting from the adjoining zinc cylinder. The porous cup containing tho 
platinum is rilled with strong nitric acid, and the outer vessel containing tho 
zinc with weak sulphuric acid. Fig. 70 represents a series of these cups, 
arranged to form a compound cir- 
cuit, with their terminal poles, P 
and Z. This form of battery is 
objectionable on account of the 
corrosive character of tho acids 
employed, and the deleterious va- 
pors that arise from it when in 
action. 

In what is known as Bunsen's 
Carbon Battery, a cylinder of 
carbon is substituted, on the 
ground of economy, in place of 
the platinum plates of Grove's battery. 

237. Resistances to the Circulation of the Galvanic 
Current . — The amount of force or of electricity which circulates in a gal- 
vanic circuit does not depend wholly upon the energy of the chemical action 
which is exerted between the generating metal and the exciting liquid. 
" The current experiences a retardation or resistance from the very conduc- 
tors by which its influence is transmitted ; just as in the transmission of 
mechanical force in an arrangement of machinery, the intervention of the 
pivots and levers which are required for its conveyance introduces ad- 
ditional friction and additional weight, which are required to be overcomo 
or moved, and which thus diminish the efficient power of the machine." — 
Miller. ,, 

' The resistances of the galvanic current arise from the imperfect conduct- 
ing power of the liquid which is employed to excite it, and of the plates, 
wires, etc., the resistance offered by the liquid being the more considerablo 




Questions— Describe Grove's battery. Is tbe electricity of a galvanic circuit always 
in proportion to the chemical action exerted ? What are the resistances it experiences ? 
To what are these resistances proportional ? 

V 



146 PRINCIPLES OF CHEMISTRY. 

of the two. The further the plates are removed from each other in the liquid, 
and the longer the column of imperfectly conducting matter which the elec- 
tricity is obliged to traverse, the greater the resistance. The same thing is 
also true of the conducting wire. A wire one tenth of an inch in diameter, 
will for equal lengths oiler four times the resistance of a wire two tenths, or 
one fifth of an inch thick. 

238. Characteristics of Ordinary and Galvanic Elec- 
tricity. — Electricity in its ordinary manifestations, as 
•when developed by friction or by an electrical machine, 
exhibits itself in sudden and intermitted shocks, accom- 
panied with a sort of explosion ; galvanic electricity, or 
electricity produced by chemical action, is, on the contrary, 
a steady flowing current. 

The electricity evolved by a single galvanic circle is 
great in quantity, but weak in intensity. 

The electricity, on the contrary, produced by friction, 
or that of a thunder-cloud, is small in quantity, but of 
high tension, * or intensity. 

These two qualities may be compared to heat of different temperatures. A 
gallon of water at a temperature of 100° has a greater quantity of heat than 
a pine at 200° ; but the heat of the latter is more intense than that of the 
former. Again, in the phosphorescence of the sea, which often spreads over 
thousands of miles, we have an illustration of light very feeble in intensity, 
but enormous in quantity. 

239. Quantity and Intensity, how Measured . — "We meas- 
ure the quantity of electricity in many ways ; but most conveniently by the 
amount of any chemical compound which it can decompose. A machine or 
battery, for example, which, when arranged so as to decompose water, evolves 
from it four cubic inches of oxygen and hydrogen in one minute, is furnishing 
twice the quantity of electricity supplied by an apparatus which evolves only 
two cubic inches of the gases in the same time. 

The intensity of electricity is less easily measured ; but it is comparatively 
indicated by the ease with which it can travel through bad conductors ; by 



* " Tension is merely a synonyme for intensity, which originated in the hypothesis of 
electricity being an elastic fluid, which might be regarded as existing in a thunder-cloud, 
or on the conductor of a friction-machine in a state of condensation or compression, like 
high-pressure steam struggling to escape from a boiler, or air seeking to force its way out 
of the chamber of an- air-gun. The word tension has been preferred to intensity, simply 
on account of its brevity, and its convenience in forming a double noun with electricity. 

QtTESTiOsrs. — What are the characteristic differences between galvanic and ordinary 
electricity? To what m/iy quantity and intensity be compared? How are there two 
qualities measured? What is understood by the term tension ? 



ELECTRICITY. 147 

its power to overcome energetic chemical affinity, such as that which binds 
together the elements of water ; by the length of space across which it can 
pass through dry air (as in the case of a lightning flash striking a tree from a 
great distance) ; by the attractions and repulsions it produces in light bodies ; 
and by the severity of the shock it occasions to living animals. 

Galvanic electricity will traverse a circuit of 2,000 miles of wire, rather 
than make a short circuit by overleaping a space of resisting air not exceed- 
ing one hundredth part of an inch. Frictional electricity, on the other hand, 
will force a passage across a considerable interval, in preference to taking a 
long circuit through a conducting medium. 

The assertion is within bounds, that the whole electricity of a destructive 
thunder-storm would not suffice for the electro-gilding of a single .pin — so in- 
significant is its amount. A small copper wire, dipped into an acid along 
with a wire of zinc, would evolve more electricity in a few seconds than the 
largest friction electrical machine, kept constantly revolving, would furnish 
in many weeks. No shock, on the other hand, would be occasioned by the 
electricity from the immersed wires ; nor would it produce a spark, or de- 
compose water — so low is its intensity. A galvanic battery of many plates 
will, however, produce electricity of sufficient intensity to kill a large animal, 
and produce other effects analogous to lightning. 

Electricity of intensity then, or tension-electricity, is 
electricity characterized by the greatness of its intensity—, 
or whose intensity is greater than its quantity. Electricity 
of quantity, on the other hand, has its quantity greater 
than its intensity. 

The intensity diminishes as the quantity increases ; but the ratio which the 
one bears to the other differs through a very wide scale, so that a knowledge 
of the degree of the one does not often enable us to predicate the amount of 
the other. Practically, we have no difficulty in reducing both to a minimum, 
or in exalting the one whilst we reduce the other ; but we can not at once 
exalt both intensity and quantity. The discovery of a method of effecting 
this will make a new era in the science ; and admit of the most important 
applications to the useful arts. 

240. Practical Applications of Electricity of Quan- 
tity and Intensity — In the arts, it depends much upon the purpose 
to which electricity is to be applied whether it should be chosen great in 
quantity, or great in intensity. If the chemist desires to analyze a gaseous 
mixture by exploding it, he will use an electrical machine to supply a mo- 
mentary spark of great intensity. But the electro-plater, who has constantly 
4o decompose a compound of gold or silver, employs a small voltaic battery — 
which furnishes great quantities of electricity of considerable intensity. The 

Questions. — Illustrate the differences between quantity and intensity. What definition 
may be given of the two ? What relation exists between them ? What are their practical 
applications ? 



148 PRINCIPLES OF CHEMISTRY. 

electric light requires both quantity and intensity to be very great. The 
electric telegraph demands great quantity, but the. intensity need not be very 
high. 

241. Electro- chemical Decomposition.— When a current 
of galvanic electricity is made to pass through a compound 
liquid, composed of one conducting and one non-conduct- 
ing substance, its tendency is to decompose and separate 
it into its constituent parts. 

242. Decomposition of Water . — The most remarkable illustra- 
tion of this power is to be found in the decomposition of water. This sub- 
stance is composed of two gases, oxygen and hydrogen, united in the propor- 
tions of one measure of the former to two of the latter. "When two gold or 
platinum wires, connected with the opposite ends of a galvanic battery, are 
placed in water at a short distance from each other, the water is decomposed, 
the hydrogen arising in bubbles from the negative pole of the battery, and 

the oxygen from the positive pole. When two glass tubes 
are placed over the platinum poles, as is represented in Fig. 
Tl, we can collect the bubbles as they rise, the volume of the 
hydrogen being twice as great as that of the oxygen. 

When copper wires, or the wires of metals which tend 
strongly to unite with oxygen are employed, gas escapes from 
one wire only ; whilst if platinum or gold wires be used, gas 
5- is evolved from both. In the first case, the oxygen combines 
with the copper or other oxydizable metal, and forms an 
oxyd, which is dissolved by the liquid, and therefore hydro- 
gen alone escapes ; in the second case, both gases are evolved, 

since neither platinum nor gold has sufficient chemical affinity for oxygen to 

combine with it at the moment of its liberation. 

243. Electrodes . — The term electrode is often used to designate the 
poles of a galvanic battery. It is especially applied in those cases in which 
the connecting wires of a circuit are terminated with strips of platinum, gold, 
charcoal, or some other good conducting, non-oxydizable substance. 

244. Theory of Electro-chemical Decomposition.— 
Scientific men are not fully agreed upon the explanation of the phenomenon 
of chemical decomposition by means of the galvanic current. A general idea 
of what takes place may perhaps be best gained from what is called the 
electro-chemical theory. According to this, chemical attractions, which wo 
distinguish by the name of affinity, and electrical attractions depend on the 
same cause, acting in one case on atoms, and in the other on masses of mat- 
ter. Every atom of matter is regarded as charged in respect to all other 



QtTEBTioxe. — What is the influence of the electric current in producing electro-chemical 
decomposition ? How is this illustrated in the decomposition of water ? What are elec- 
trodes ? What is the theory of the decomposing action of galvanic electricity ? 




ELECTRICITY. 149 

atoms, with either positive or negative electricity. In the case of "water, 
hydrogen is the electro-positive element and oxygen the electro-negative ele- 
ment. It has been already shown that bodies in opposite electrical states are 
attracted by each other. Hence, when the poles of a galvanic battery are 
immersed in water, the negative pole will attract the positive hydrogen, and 
the positive pole the negative oxygen. If the attractive force of the two 
electricities generated by the battery is greater than the attractive force which 
unites the two elements, oxygen and hydrogen, tejjether in the water, the 
compound will be decomposed. Upon the same principle other compound 
substances may be decomposed, by employing a greater or less amount of 
electricity. In this way Sir Humphrey Davy made the discovery that potash, 
soda, lime, and other bodies, were not simple in their nature, as had pre- 
viously been supposed, but compounds of a metal with oxygen. 

This theory, as presented, is not received as strictly in accordance with the 
fact. Recent experiments of Faraday have proved that the electricity which 
decomposes, and that which is evolved by the decomposition of a certain 
quantity of matter, are alike. Thus, water is composed of oxygen and hydro- 
gen ; now, if the electrical power which holds a grain of water in combina- 
tion, or which causes a grain of oxygen and hydrogen to unite in the right 
proportions to form water, could be collected and thrown into a voltaic cur- 
rent, it would be exactly the quantity required to produce the decomposition 
of a grain of water or the liberation of its elements, oxygen and hydrogen. 

The quantity of electricity, however, which is required to effect chemical 
decomposition is enormous. Faraday estimates the amount of electricity re- 
quired to decompose a single grain of water to be equal to that evolved by a 
powerful flash of lightning. 

245. Limits of the Decomposing Action. — Decomposition 
by the agency of the electric current takes place solely at 
those points where the electricity enters and leaves the 
liquid. 

Thus, when a portion of water, for example, is subjected to decomposition 
in a glass vessel with parallel sides, oxygen is disengaged at the positive 
electrode, and hydrogen at the negative, the gases being perfectly pure and 
unmixed. If, while the decomposition is rapidly proceeding, the intervening 
water is carefully examined, not the slightest disturbance or movement of 
any kind will be perceived ; nothing like currents in the liquid, or transfer of 
gas from one part to the other can be detected ; and yet two portions of 
water, separated by an interval of four or five inches, may be respectively 
evolving pure hydrogen and oxygen. Now, since we know that every par- 
ticle of water is composed of oxygen and hydrogen in the exact ratio of two 

Questions. — Explain the decomposition of -water. What fact has been proved by the 
experiments of Faraday? What is the relative quantity of electricity required to effect 
chemical decomposition ? At what points of the galvanic circuit does the decomposing 
action take place ? Illustrate this. In what respect is this action contrary to what might 
be naturally expected ? 



150 PRINCIPLES OF CHEMISTRY. 

measures of the latter to one of the former, it would naturally be supposed 
that the electric current having separated the oxygen at one point, hydro- 
gen would, having lost its combining element, also escape at the same point. 
This, however, is not the case, and great difficulty has been experienced in 
accounting for it. 

The difficulty will be more evident, says Mr. Hunt, if we take the experi- 
ment on a larger scale ; for example, if on one side of a wide river the 
positive pole is placed in the water, and the negative pole on the other, we 
shall still have — the battery being of sufficient power — oxygen given off on. 
one side of the river, while hydrogen would be evolved at the other. 

The following is the received explanation : — The arrangement of the par- 
ticles constituting a line or layer of water between the poles of a galvanic 
circuit may be represented as follows, the positive atom, hydrogen, of each 
particle of water being turned by the influence of the electricity toward the 
negative pole, and the negative atom, oxygen, toward the positive pole — 

Positive pole — OH, OH, OH, OH, OH, OH — Negative pole. 

The same thing may be also illustrated in Fig. 72, where the particles of 
„ ^ water are supposed to be spherical, the shaded 

portion of each sphere representing the hydro- 
gen half of the particle, and the light portion 

-^ci(xw<K»^ ,ho Tr o H yseal ; alc ,'•-,* «.■,•%, 

-"- a • If the positive pole is placed on the left and 

the negative on the right, oxygen passes off 

from the first, and hydrogen from the last ; if 
we reverse the poles, the order of the decomposition is changed also. It is 
not, however, to be supposed that when H. is liberated from 0. at the nega- 
tive pole, that the 0. of that particle passes over along the line to the positive 
pole ; but the view taken is, that as soon as the atom of oxygen loses its 
hydrogen, it combines with the atom of hydrogen of the next particle of 
water, and a new particle of water is reproduced. The oxygen of the second 
particle being thereby liberated, combines with the hydrogen of the next 
particle of water, and thus the decomposition and recomposition is continued 
on to the end of the series. Resorting again to symbols, No. 1 will repre- 
sent the state of things before any change has been effected, and No. 2 the 
change after the circuit is complete — 

No. l.+OH, H, OH, OH, H - 

No. 2. + 0, H 0, H 0, H 0, H 0, H — 

It should also be borne in mind, that the changes described are not suc- 
cessive, but simultaneous at each end of the series of particles, and at all 
intervening points in the line of the series. ~^ >> J 

246. Electrolysis and Electrolytes, — The process ofre^ 
solving compounds into their constituents by electricity is 

Questions. — "What is supposed to actually occur in the decomposition of water ? What 
Is electrolysis ? 



ELECTRICITY. 151 

termed Electrolysis, and a body susceptible of such de- 
composition is termed an Electrolyte. 

No elementary substance can be an electrolyte ; for from the nature of the 
process, compounds alone are susceptible of electrolysis. Electrolysis occurs 
only whilst the body is in the liquid state. The free mobility of the particles 
which form the body undergoing decomposition is a necessary condition of 
electrolysis, since the operation is always attended by a transfer of the com- 
ponent particles of the electrolyte in opposite directions. 

The passage of a current of electricity through the liquid used in the cells 
or cups of a galvanic circuit depends upon the decomposition of its particles, in 
the same manner as in the case of water. No fluid, therefore, which is not 
an electrolyte, or in other words, which is not capable of being decomposed, 
is suitable for exciting a battery. 

247. Electro-chemical Order of the Elements.— All the 
elementary substances, according as they appear at the posi- 
tive or negative poles of a galvanic circuit, have been classi- 
fied into electro-positive and electro-negative rubstances. 

In the following table the most important of the elements are rrranged in 
the order of their relative negative and positive properties, the most ii tensely 
negative element being placed at the top of the series, and the most intensely 
positive at the bottom : 

Electro-negative. — Oxygen. 

Sulphur. 

Nitrogen. 

Chlorine. 

Fluorine. 

Carbon. 

Phosphorus. 

Hydrogen. 

Gold. £-~~"~~ 

Platinum. 

Mercury. 

Silver. 

Copper. 

Tin. 

Lead. 

Iron. 

Zinc. 

Sodium. 

Potassium. — Electro-positive. 

Questions. — What are electrolytes? Why can not an elementary substance be an elec- 
trolyte ? What conditions are necessary for electrolysis ? What fluids only are capable 
of exciting a galvanic battery? How may the elementary substances be classed as re* 
epects their electrical properties ? 



152 PRINCIPLES OF CHEMISTRY. 

In this arrangement, each metal is positive as respects all that stand before 
it, and negative as respect those that succeed it. Oxygen is negative in every 
combination, and potassium appears to be uniformly positive. Hydrogen is 
highly positive when compared with oxygen and chlorine, but with metals it 
always exhibits negative electric energy. 

248. Electro-metallurgy, or electro typing, is the art or 
process of depositing, from a metallic solution, through 
the agency of galvanic electricity, a coating or film of 
metal upon some other substance.* <r 

The process is based on the fact, that when a galvanic 
current is passed through a solution of some metal, as of 
sulphate of copper (sulphuric acid and oxyd of copper), 
decomposition takes place ; the metal, being electro-posi- 
tive, attaches itself in a metallic state to the negative 
pole, or to any substance that may be attached to the 
negative pole ; while the oxygen, or other electro-nega- 
tive element before in combination with the metal, goes 
to, and is deposited on the positive pole. 

In this way a medal, a wood-engraving, or a plaster cast, if attached to the 
negative pole of a battery, and placed in a solution of copper opposite to the 
positive pole, will be covered with a coating of copper ; if the solution con- 
tains gold or silver instead of copper, the substance will be covered with a 
coating of gold or silver in the place of copper. 

The thickness of the deposit, provided the supply of the metallic solution 
be kept constant, will depend on the length of time the object is exposed 
to the influence of the battery. 

In this way, a coating of gold thinner than the thinnest gold-leaf can be 
laid on, or it may be made several inches or feet in thickness, if desired. 

The usual arrangement for conducting the electrotype process is represented 
by Fig. 73 It consists of a trough of wood, or an earthen vessel, containing 
the solution of the metal, the decomposition of which is desired — for example, 
sulphate of copper. Two wires, one connected with the positive, and the 
other with the negative pole of a battery, Q, are extended along the top of 
the trough, and supported on rods of dry wood, B and D. The medal, or 
other article to be coated, is attached "to the extremity of the negative wire 



* The general name of electro-metallurgy includes all the various processes and results 
which different inventors and manufacturers have designated as galvano-plastic, electro- 
plastic, galvano-type, electro-typing, and electro-plating and gilding. 



Qukstio-ns. — What substance is always negative? What one always positive? Define 
electro-metallurgy. Upon what is the process hased ? How is the thickness of the de- 
posit regulated ? Describe the arrangement for conducting the electrotype process. 



ELECTRICITY 



153 



and a plate of metallic copper to the end of the positive wire. "When both 
of these are immersed in the liquid, the action commences — the sulphate of 
copper is decomposed — the copper being deposited on the medal attached 
to the negative pole, and the oxygen, before combined with it, on the copper 
plate attached to the positive pole, forming oxyd of copper. As the with- 
drawal of the metal from the solution goes on, the oxyd of copper thus formed 

Fig. 13, 




unites with the sulphuric acid which is liberated in the solution, and forms 
sulphate of copper. This dissolving in the liquid, maintains it at a constant 
strength. 

The sole object of attaching a plate of metallic copper to the positive pole 
is to thus preserve the strength of the solution of sulphate of copper. If the 
positive pole had terminated with a plate of platinum or gold, the action 
would have commenced equally well, but the oxygen liberated from the cop- 
per, through its want of affinity to either the platinum or the gold, would 
have escaped as gas, and the solution gradually becoming weaker from the 
withdrawal of its elements, the electro-plating action would cease. When the 
operator judges that the deposit on the medal is sufficiently thick, he removes 
it from the trough, and detaches the coating. The deposit is prevented from 
adhering to the medal by rubbing its surface in the first instance with oil, or 
black-lead, and if it is desired that any part of the surface should be left un- 
coated, that portion is covered with wax, varnish, or some other non-con- 
ductor. 

In this way a most perfect reversed copy of the medal is obtained — that is, 
the elevations and depressions of the original are reversed in the copy. To 
obtain a fac-simile of the original, the electrotype cast is subjected to a repe- 
tition of the process. 

In general, it is found more convenient to mold the object to be repro- 
duced in wax, or Plaster of Paris. The surface of this cast is then brushed 
over with black-lead to render it a conductor, and the metal deposited directly 
upon it. The deposit obtained will then exactly resemble the original ob- 
ject. H* 



154 PRINCIPLES OF CHEMISTRY. 

The pages and engravings in the book before the reader are illustrations of 
the perfection and practical application of the electrotype process. .The en- 
gravings were first cut upon wood-blocks, and then, in combination with the 
ordinary type, formed into pages. Casts of the whole in wax were then 
made, and an electrotype coat of copper deposited upon them, and from the 
copper plates so formed the book was printed. The great advantage of this 
is, that the copper being harder than the ordinary type metal, is more durable, 
and resists the wear of printing from its surface for a longer period. 

The improvement effected by electro-metallurgy in engraving is very great. 
When a copper plate is engraved, and impressions printed off from it, only the 
first few, called "proof impressions," possess the fineness of the engraver's 
delineation. The plate rapidly wears and becomes deteriorated. But by the 
electrotype process, the original plate can at once be multiplied into a great 
many plates as good as itself, and an unlimited number of the finest impres- 
sions procured. 

In this way the map plates of the Coast Survey of the United States, some 
of which require the labor of the engraver for years, and cost thousands of 
dollars, are reproduced — the original plate being never printed from. 

The metals upon which an adherent coating of silver or gold is most 
readily deposited are brass, copper, bronze, and German silver. The articles 
to be plated or gilded must be carefully cleansed from ail adhering greasy 
matters by boiling them in a weak alkaline solution, and then rubbing them 
with chalk, rotten-stone, etc. The articles are then carefully washed, at- 
tached to a clean copper wire, and immersed in the silvering solution. The 
deposit is hastened by keeping the solution moderately warm, especially at 
the commencement of the process. The articles, when plated, have a dead 
white, or chalky appearance, but by burnishing they assume the brilliant lus= 
ter of polished silver.* 

249. Protection of Metals from Corrosion,— When two 
metals which are positive and negative in their electrical 
relations to each other, are brought in contact, a galvanic 
action takes place which promotes chemical change in the 
positive metal, but opposes it in the negative metal. 

Thus, when sheets of zinc and copper immersed in dilute acid touch each 
other, the zinc oxydizes or rusts more, and the copper less rapidly, than 



* The teacher, for experiment, can best illustrate the deposition of metals by electro- 
chemical action in the following manner ; — Put a piece of silver in a glass containing a 
solution of sulphate of copper, and into the same glass insert a piece of zinc. No change 
will take place in either metal so long as they are kept apart ; but as soon as they touch, 
the copper will be deposited upon the silver, and if it <he allowed to remain, the part im- 
mersed will be completely covered with copper, which will adhere so firmly that mere 
rubbing alone will not remove it. 

Questions. — How has the electrotype process affected the art of engraving ? What are 
the peculiarities of the process of electro-plating ami gilding ? T T n<Wwhat n'rcnmptanrns 
can metals he protected from chemical notion ? Illustrate thin. 



ELECTRICITY. 155 

without contact. Iron nails, if used in fastening copper sheathing to vessels, 
rust much quicker than when in other situations, not in contact with the 
copper. The reason of this is, that the two metals, in consequence of the 
electricity developed by their union, are placed in opposite electrical condi- 
tions. The copper which is ordinarily positive, is rendered negative by the 
contact of the zinc, or iron ; it, therefore, is not only entirely wanting in at- 
traction for the negative corroding oxygen of the air, or water, on the prin- 
ciple that bodies similarly electrified repel each other, but even has a tendency 
to abandon any oxygen with which it may have previously combined. The 
zinc and iron, on the contrary, in virtue of the exaltation of their naturally 
positive condition, combine with the negative oxygen most readily, on the 
principle that bodies in the opposite electrical condition attract each other. 
The positive metal, therefore, oxydizes most speedily, while the negative 
metal remains uninjured. 

What is called galvanized iron, is iron covered entirely, or in part, with a 
coating of zinc. The galvanic action between the two oxydizes the zinc, 
but protects the iron from rust. Sir Humphrey Davy attempted to apply this 
principle to the protection of the copper sheathing of ships (which wastes 
rapidly through the action of the oxygen in sea-water), by placing at inter- 
vals over the copper small strips of zinc. The experiment was tried, and a 
piece of zinc as large as a pea was found adequate to preserve forty or fifty 
square inches of copper ; and this wherever it was placed, whether at the 
top, bottom, or middle of the sheet, or under whatever form it was used. 
The value of the application was, however, neutralized by a consequence 
which had not been foreseen ; since the protected copper bottom rapidly ac- 
quired a coating of sea-weeds and shell-fish, whose friction on the water 
became a serious resistance to the motion of the vessel. The adhesion of 
these, under ordinary circumstances, is prevented by the corrosion cf the 
copper by oxygen, and by the poisonous action of the compounds of ccpper 
and oxygen which are thereby formed. 

The principle, however, has been applied with success for the protectee 
of iron pans used in evaporating sea-water, and in other similar apparatus 

Questions. — How is this action accounted for? What is galvanized iron? Y. r ^:/: 
practical application of this principle was attempted by Sir Humphrey Davy? 



INORGANIC CHEMISTRY. 



That department of Chemistry which treats of inor- 
ganic, or unorganized bodies, is termed Inorganic Chem- 
istry. 

It includes the doctrines of affinity, the laws of combi- 
nation, the chemical history of the elementary bodies, and 
of those compounds of the elements which are not the pro- 
duct, either directly or indirectly, of living, organized bodies. 



CHAPTER V 



THE GENERAL PRINCIPLES OF CHEMICAL PHILOSOPHY. 

250. Elements. — A chemical element is a material sub- 
stance not yet analyzed or taken apart — not yet resolved 
by any process into two or more bodies differing from 
itself. 

No one substance within the reach of man is, however, positively known to 
be elementary ; and the student should distinctly understand, that it can not 
rightly be inferred, because a body has not yet by any known process been 
decomposed, that it never will be. 

251. Number of the Elements. — The number of elements 
at present fully recognized by chemists is sixty-two. Of 
these only twenty-nine were known at the commencement 
of the present century.* 



* This fact will illustrate to the general student one great feature in the progress of 
modern chemistry ; but to the chemist, the discovery of thirty-three new elementary 



Questions. — What is inorganic chemistry ? What is a chemical element ? Is any sub- 
stance positively known to be elementary ? What is the number of the elements ? 



PRINCIPLES OF CHEMICAL PHILOSOPHY. 157 

252. Classification of the Elements.— The elements are 
usually divided into two great classes, the metallic and 
non-metallic substances, or the Metals and the Metalloids. 
The substances comprised in the first class are the more 
numerous, but those in the latter are the more abundantly 
distributed.* 

Of the sixty-two elements, five are gases, viz., oxygen, hydrogen, nitrogen, 
chlorine, and fluorine ; two are simple liquids, mercury and bromine ; the re- 
mainder are solids, at common temperatures. Only fourteen of Ihe elements 
are of common occurrence, and of these the great mass of the earth, with its 
atmosphere and water, are composed. The remainder occur only in com- 
paratively small quantities, and fully one third of the whole number are so 
rare as not to admit of any useful application. 

A very few only of the elements are found naturally in a free or uncom- 
bined state ; of such we may mention oxygen and nitrogen, existing in the 
atmosphere ; sulphur, carbon, and a few of the metals, as gold, platinum, 
copper, etc., distributed throughout the earth. The majority exist only in 



bodies implies an amount of laborious and protracted researcb, preceding and following 
each discovery, of which words can convey to the uninitiated no adequate idea. 

* The alchemists regarded the metals, the only elementary bodies with which they were 
acquainted, as compound substances. The baser metals, as lead, iron, copper, etc., they 
believed to contain the same elements as gold, from which they differed on account of 
their association with impurities ; these impurities being separated, it was imagined that 
gold would remain. 

The problem, known as the " transmutation of metals," which they sought to solve, and 
labored for centuries to effect, was not to generate or create metals, but to change the 
proportion of the elementary substances which composed them. "For a century or 
more," says Professor Faraday, in a recent lecture, " it has been the custom to spurn the 
doctrines of the alchemists as devoid even of the semblance of philosophic truth. The 
time has, however, past for this opinion to be maintained, and within the last few years a 
series of manifestations have been noticed which go far to vindicate many of their opinions." 
At a meeting of the British Association for the Promotion of Science in 1851, M. Dumas 
and Professor Faraday both avowed their belief in the possibility of transmutation, and 
the latter stated that he had even experimented with a view of producing this result, 
and should continue to do so. It is not, however, to be understood that chemists ex- 
pect transmutation will be effected in exactly the sense of the old alchemical philosophy. 
There is no evidence that lead can be converted into silver, or copper into gold. M. Du- 
mas suggests that the first successful transmutation as regards metals will be to effect a 
change of physical state merely, without touching chemical composition; thus, already 
we have carbon, which, as the diamond and as charcoal, manifests two widely different 
states. Sulphur also assumes two forms, as also phosphorus, silicon, and boron. Then 
why not a metal ? 

Within a very recent period (1857), a series of experiments have been published by Dr. 
Draper of New York, which seem to indicate that silver is capable of transmutation into 
another metal, possessing some of the properties and characteristics of gold. " It is hard 

Questions. — Into what two great classes are the elements usually divided ? How many 
of the elements are gaseous ? How many liquid ? How are the elements distributed in 
nature ? In what condition are they generally found ? 



158 INORGANIC CHEMISTRY. 

combination with each other, and in this condition they are so completely dis- 
guised as to manifest few or none of their characteristic properties. 

253. Compound Bodies. — All compound bodies are formed 
by the chemical union of two or more of the elementary 
substances. 

The compounds so resulting are, as might be supposed, almost innumer- 
able, and the progress of research is continually adding to their number. 
Many of the compounds artificially formed by chemical action have no exist- 
ence in nature. Some of them are of eminent utility to man, while others 
possess properties of a strange and fearful character. Happily, however, the 
majority of those compounds which are especially deleterious are, by the dif- 
ficulty and expense of their preparation, placed far beyond the reach of the 
majority of mankind. 

. 254. Cause of Chemical Combination . — In the early days 
of chemist^, chemical combination between different substances was supposed 
to take place through the agenc3 r and guidance of some spiritual or super- 
natural power which invested, or dwelt in every form of matter, both ani- 
mate and inanimate. The popular names of many chemical substances at tbo 
present time, such as spirit of wine, spirit of nitre, etc., are evidences of the 
former general credence in this doctrine. Stahl, a noted chemist who died in 
1685, taught that chemical combination proceeded from an approximation of 
the combining parts, somewhat after the manner of wedges. Modern chem- 
istry explains chemical combination between different substances, as occur- 
ring through the agency of an attractive force, acting only between the atoms, 
or molecules of dissimilar substances, and only at insensible distances. This 
force, to distinguish it from other forms of attraction, is termed affinity. To 

to think," says Sir David Brewster, " that the so-called elements are truly simple. The 
instinct of humanity revolts against believing that the Maker has departed from his 
wonted simplicity of procedure in this one part of creation, and flung such a number of 
unchangeable elements from his immediate hand. Many thoughtful and ingenuous men, 
indeed, have frankly supposed that it were more like the nature of Deity, as shown by 
his interpreted works, to pour forth the unreckonable variety of things from the bosom 
of one or two principles. ThaleB and the Greek physicists, Roger Bacon, Stahl, Lavoi- 
sier, Sir H. Davy, and Berzelius, have all given more or less expression to this idea. The 
greatest question in chemistry, or in plain earnest, the one question of the age then, is 
precisely this : — What is the interior nature of these elements ? Science bids us ask, and 
perhaps nature is ready to answer it ; but what shall be done, since no analytical power 
can -move one of those steadfast natures from its propriety ? Let synthesis be tried if 
analysis has failed ; synthesis has never been tried. It is in the highest degree probablo 
that all the present elements are equi-distant from simplicity, and all equally compound, 
if there be any truth in the unanimous testimony of chemical analogy. Their case is ex- 
actly like that of potassa, soda, lime, and their congeners, before the discovery of potas- 
sium ; — that is to say, pota6sa once discovered to be metallic oxyd, all the rest were clearly 
metallic oxyds too, as experiment was not long of showing. In the same way, if the secret 
of one of these silent, tantalizing elements be discovered, the secret of them all is out." 

Questions. — How are compound bodies formed ? Do all the compounds known to the 
chemist exist in nature? How did the. cnrly chemists explnin rh^miral comhinnHrm? 
[low does modern chemistry explain it ; 



PRINCIPLES OF CHEMICAL PHILOSOPHY. 159 

the question ""What is the attractive force thus designated?" no satisfactory 
answer can be given. There are, however, some reasons for supposing it to 
be a modification of electrical force. 

255. Characters of Chemical Affinity.— Chemical af- 
finity is distinguished from all other kinds of attractive 
forces which act at minute distances, hy certain peculiar 
characteristics. These are briefly as follows : — ■ 

T. It is exerted within its own limits with intense en- 
ergy, but beyond those limits it is entirely powerless. 

An iron wire which will support a weight of a thousand pounds without 
breaking, will in a few minutes yield to the almost noiseless action of a mix- 
ture of sulphuric acid and water. The tenacious metal will dissolve — particle 
by particle will be detached from the iron — and in the clear liquid which re- 
sults, no vestige of the structure of the metal will remain. It is rarely possi- 
ble by minute subdivision to cause the particles of different substances to 
approximate sufficiently near to produce chemical action. Tartaric acid and 
carbonate of soda nlay be incorporated by grinding for hours in a mortar, 
but they will not act chemically upon each other. If, however, we add a 
portion of water, which dissolves the particles of both and allows them mu- 
tually to approach closer, a chemical union, accompanied by an effervescence, 
immediately takes place. 

The amount of power or work produced by the action of chemical affinity 
is in general very great, and in some instances we may approximately meas- 
ure and compare it with other forces. For example, coal burns and produces' 
heat solely in consequence of the affinity, or attractive force, which causes 
particles of oxygen in the air to unite with particles of coal. Now, a pound 
of the purest coal, burned under the proper circumstances, and its resulting 
heat applied to the production of steam, will generate a power capable of 
lifting a weight of 100 pounds to a height of 20 miles, or 1 pound 2,000 miles. 
This result, therefore, is a measure of the chemical force of affinity which 
operates between the particles of a pound of coal and the quantity of oxygen 
that unites with them. 

II. It is only exerted between dissimilar substances. 

No manifestations of this force can take place between two « pieces of iron, 
two pieces of copper, or two pieces of sulphur ; but between sulphur and 
copper, or sulphur and iron, chemical action of the most energetic kind may 
occur. 

Were there but one kind of matter in the universe, the force of affinity 
could not exist ; no chemical action could take place, and the science of 
chemistry would be unknown. 

Questions. — What do we know of the nature of affinity? State and illustrate the first 
characteristic of affinity ? What is said of the amount of work, or power which chemical 
affinity is oapahlp of prnn'n<"in<r 9 Give an illustration. State and illustrate Hip spponrt 



160 



INORGANIC CHEMISTRY. 



III. Generally speaking, the greater the difference in 
the properties of bodies, the greater is their tendency to 
enter into chemical combination. Between bodies of a 
similar character, the tendency to union is feeble. 

IV. Chemical affinity occasions an entire change in the 
properties of the substances acted upon. 

This change is most remarkable, and is of such a character as could not 
be predicted from any acquaintance with the substances in a separate condi- 
tion. Thus, if we dissolve copper in sulphuric acid, we obtain a blue, semi- 
transparent substance ; while iron treated in the same manner, yields a light 
green product. 

Although in a combination, the properties of the constituents are changed, 
and, as far as ordinary observation is concerned, are destroyed, yet they really 
exist in the compound, and can be again reproduced by restoring the com- 
bining elements to their original condition. 

V. The power of affinity is exerted between different 
kinds of matter with different, but definite degrees of 
force. 

Nitric acid, for example, will combine with and dissolve most of the metals, 
as silver, mercury, copper, and lead ; but it unites with them with very dif- 
ferent degrees of intensity. With silver the combination is less powerful than 
with mercury, less so with mercury than with copper, and with copper less 
again than with lead.* Indeed, the different elements may be arranged in 
tables, in such a way as to indicate by their order the degree of affinity which 
they respectively have for some particular element. 



* The difference in the strength of the affinity exist- 
ing between different substances may be easily illus- 
trated by the following experiment: — Dissolve a few 
crystals of acetate of lead (sugar of lead) in a small 
quantity of water, and fill a phial with the solution. If 
a piece of zinc be now suspended in the liquid, it will, 
after a little time, become covered with a gray coating, 
from which brilliant metallic spangles will gradually 
shoot forth (see Fig. 74) somewhat in the 6hape, of a 
tree. These are pure lead, and the phenomenon is fa- 
miliarly known as the lead tree. The effect thus pro- 
duced is due to the superior affinity of the zinc for the 
acetic acid combined with the lead, which causes the 
two metals to interchange places — i. e., the zinc combin- 
ing with the acid and entering into solution, and the lead 
being deposited in a metallic state, in place of the zinc. 
If the action be kept up sufficiently long, every particle of lead may be in this way with- 
drawn from the liquid. 




Questions. — What is the third characteristic of affinity ? What is the fourth ? Illus- 
trate this. Is the force of affinity always uniform ? How may this be shown ? 



PRINCIPLES OF CHEMICAL PHILOSOPHY. 161 



VI. However much the properties and form of bodies 
may be changed by the action of chemical affinity, no de- 
struction of matter ever ensues — the weight of the pro- 
ducts of combination being always exactly equal to that 
of the component elements before combination. 

By means of a simple experiment it may be shown that even although a 
substance may, through the action of chemical affinity, vanish from our sight, 
it still continues to exist as a gas which has the same weight as the visible 
solid which furnished it. Into a glass flask, A, Fig. 15, of about 250 cubic 
inches capacity, which is provided with a brass cap and stop-cock, 10 or 12 
grains of gun-cotton are introduced. The air in the flask is then completely 
exhausted by means of an air-pump, and the flask weighed. The cotton is 
then ignited by means of two wires, a and b, proceeding from a galvanic bat- 
tery, and passing through the cap of the flask. p IG> ^ 
On the transmission of a voltaic current, the 
cotton entirely disappears with a brilliant 
flash, but the flask, if weighed again, will be 
found to be as heavy as before the cotton was 
fired. 

VII. Chemical combination of 
substances may either occur in- 
stantly on mixture, or may be in- 
definitely postponed until some 
other force, as heat, for example, 
produces a commencement of the 
action. 

In a large proportion of cases, chemical ac- 
tion will not commence spontaneously. A heap of charcoal will remain un- 
altered in the air for years ; but if a few pieces be made red hot and then 
thrown upon the heap, chemical combination between the charcoal and the 
oxygen of the air is commenced by the heat, and continues until the whole 
mass is burned. In other instances chemical action commences without. the 
application of any extraneous force. Phosphorus begins to burn slowly the 
instant it comes in contact with the atmosphere, and exposed to the heat of 
the sun, speedily bursts into a flame. V^ 

Ca-tal'y-sis . — The mere presence of a third body will 
sometimes awaken or excite the force of affinity between 




Questions — Is matter in its changes consequent on the action of affinity ever .de- 
stroyed ? What experiment illustrates this ? Under -what varying circumstances will 
chemical combination take place? Will chemical action between different substances 
generally commence spontaneously ? Illustrate this. What is catalysis ? 



162 INORGANIC CHEMISTRY. 

two other bodies to an extent sufficient to cause their 
union — without itself undergoing any alteration, either 
mechanical or chemical. Such an action is termed Ca- 
talysis. It is also sometimes called the action of 'pres- 
ence. 

Phenomena of this character are the most curious, and, in some respects, 
the most difficult of explanation of any in chemistry. A familiar example of 
this action is afforded us in the case of yeast, a most minute particle of which 
is able to excite fermentation in a large quantity of sugar in solution. Other 
examples will be noticed in the progress of this work. 

Nascent State . — Chemists have long recognized the fact, that bodies, 
when in the act of liberation, or separation from other substances, display 
far more energetic affinities than under ordinary circumstances. This con- 
dition is termed the nascent (from the Latin nascor, to be born,) state. 
Thus, hydrogen and nitrogen gases, under ordinary circumstances, do not 
unite if mingled in the same vessel ; but when these two gases are set free 
at the same time from the decomposition of some substance, they readily 
combine. 

VIII. Chemical compounds may be formed either by the 
direct union of their ingredients, or by the displacement 
of one substance by a different one in a compound pre- 
viously formed. 

IX. Whenever the elements unite directly with each 
other, heat is generally evolved, and in many instances, 
light also ; the amount of each being proportioned to the 
rapidity of the action. 

25G. Laws of Chemical Combinations , — It might naturally 
be supposed that chemical combination between the various elementary sub- 
stances would take place in all proportions indifferently, in the same manner 
as unlike particles of matter can be mingled together mechanically. Such, 
however, is not the case, but the relative proportions in which different ele- 
ments unite is determined by fixed laws.* 



* It should be here remarked, that the views adopted in this work are those of Bcr- 
zelius, Mitscherlich, Dumas, Hayes, and most of the leading chemists of the day— viz. 
that all mixtures of gases with gases, liquids with liquids, and all solutions proper, of 
solids in liquids, are not chemical combinations, unless they take place in definite propor- 
tions. Apparent combination in indefinite proportions, as of alcohol with water, may be 



Questions. — What is understood by the nascent state? In what two ways may 
chemical compounds be formed ? What phenomena of heat and light attend chemical 
combinations? Do substances enter into combination in all proportions? Enumerate 
the laws which regulate cheminal combination. 



PRINCIPLES OF CHEMICAL PHILOSOPHY. 163 

These laws, which are three in number, regulate the mode of combination 
of every known chemical compound, and are usually called the Law of 
Definite Proportions, the Law of Multiple Proportions, and the Law of Equiv- 
alent Proportions. ">'' 

257. Law of Definite Proportions.— In every chemical 
compound the nature and proportion of its constituent 
elements are fixed, definite and invariable. 

For instance, 100 parts of water contain 88-89 of oxygen and 11*11 hydro- 
gen. It matters not in what condition the water may exist — in springs, or 
in the ocean, in the form of ice, dew, cloud, or steam, its composition is uni- 
form and certain. When artificially prepared, by causing the gas hydrogen 
to unite chemically with the gas oxygen, the same proportions are required, 
that is, 11 "11 grains, ounces, or pounds of hydrogen must be taken for every 
88-89 grains, ounces, or pounds of oxygea If either one of the constituents 
be in excess, combination will still take place, but the excess will be rejected. 
So also in the case of other simple compounds. A piece of flint, or of clear 
quartz crystal, come from whatever source it may, yields in every 100 parts, 
48-2 of the element silicon, and 51'8 of oxygen. 

The law of definite proportions may be proved in two ways: first, by 
analysis, that is, by taking the compound apart and comparing the products 
of decomposition ; and, secondly, by synthesis, that is, by uniting the elements 
in definite proportions to form the required compound. 

Although of great simplicity, it constitutes one of the fundamental princi- 
ples upon which modern chemistry, as an exact science, rests. It enters into 
all the practical applications of chemistry to the arts, and is relied upon by 
the analyist as a means of verifying and classifying his results. It also en- 
ables us to draw a broad and clear distinction between a mechanical mixture 
and a chemical combination ; between the force of affinity and the force of 
adhesion, which produces the solution of solids in liquids. 

258. Law of Multiple Proportions . — It frequently happens 
that one elementary substance will unite with another in more than one pro- 
portion. The compounds so obtained differ greatty in their properties, but 
still preserve a simple relation to each other. The law which governs these 
relations, and which is known as the law of multiple proportions, may be 
stated as follows : — 

If the elements A and B unite together in more pro- 
portions than one, the several quantities of B, which unite 



explained by supposing that definite combination takes place between limited quantities 
of the combining substances, in the first instance, and that the compound thus formed is 
afterward mechanically mixed with the excess of either of the constituents. 



Questions. — State the law of definite proportions. What are illustrations ? How may 
this law be proved ? What is its practical value ? What is the law of multiple propor- 
tions? 



164 INORGANIC CHEMISTRY. 

with the same quantity of A, will bear a very simple rela- 
tion to each other. 

Thus we may have a series of compounds like the following: — A-f-B ; 
A-j-2 B ; A-f-3 B ; A-f-4 B ; A-f-5 B, etc., in which one part of the element A 
unites respectively with one, two, three, four and five parts of B, to form 
five different compounds, each possessing different properties. Such a simple 
series represents the five different compounds which nitrogen forms with 
oxygen — one, two, three, four and five parts (by weight) of oxygen uniting 
with one part of nitrogen. In some instances the relation is less simple, one 
or two proportions of one element combining with 3, 5, 7, etc., of another — the 
law simply requiring that the proportionals shall all be multiples of the small- 
est. Thus, compounds represented by the following formulas may exist : — 

2 A-J-3 B : 2 A-J-5 B ; 2 A-f-1 B, etc. 

In this l-£ is considered as the smallest combining proportional of B. 

259. Law of Equivalent Proportions.— When an ele- 
mentary body (A) unites with other bodies (B, C, D, etc.), 
the proportions in which B, C and D unite w T ith A, will 
represent in numbers the proportions in which they will 
unite among themselves, in case such union takes place ; 
in other words, the fixed proportions in which the ele- 
ments unite among themselves, may be represented nu- 
merically. 

Ox3'gen is an element that forms at least one definite compound with every 
other elementary substance, with a single exception. United with hydrogen 
it forms water, and 100 parts of water, as before stated, contain 88-89 parts 
of oxygen and 11 '11 hydrogen. United with the element calcium, it forms 
lime, and 100 parts of pure lime, if examined, will be found* to consist of 28*58 
parts of oxygen and 71-42 of calcium. In like manner 100 parts of potash 
contain 17*02 of oxygen and 82*98 of the element potassium. It will be 
apparent, from these illustrations, that the quantity of oxygen is not the same 
in its compounds with the different elements, and the inquiry next arises, 
does any constant relation exist between the proportions of oxygen and the 
proportions of the different elements which unite with it to form compounds ? 
The existence of such a relation may be shown in the following manner : — 
Having ascertained the proportions in 100 parts of the various compounds 
which each elementary body forms when it combines with oxygen, determine 
by calculation the proportion in which each element unites with the same 
fixed quantity of oxygen, as 8 parts, for example. A series of proportional 
numbers will thus be obtained, which will represent the ratios in which 



Questions. — Illustrate the law of multiple proportions. What is the law of equiva- 
lent proportions ? How is the law of equivalent proportions demonstrated 'i 



PRINCIPLES OF CHEMICAL PHILOSOPHY. 165 

each of the elements combines with oxygen. For example, in the case of 
water, it will be seen that for each 8 parts of oxygen, 1 part of hydrogen is 
present. 

For 8S-89 (the quantity of oxygen in 100 parts of water) : 11\L1 (the quan- 
tity of hydrogen) : : 8:1. 

So also in lime, for each 8 parts of oxygen, 20 of the element calcium are 
present. 

For 28-58 : 71-42 : : 8 : 20. 

And in potash, for every 8 of oxygen there are 39 of potassium. 

For 17-02 : 82"96 : : 8 : 39. 

In like manner it has, by careful and laborious investigation, been shown 
that the proportions which exist between oxygen and the other elements in 
their respective combinations, are capable of being represented numerically. 
Thus, 8 parts of oxygen unite with 14 of nitrogen, 16 of sulphur, 6 of carbon, 
28 of iron, 32 of copper, 100 of mercury, 104 of lead, 108 of silver, and 
so on. 

But further experiments have led to the very remarkable discovery, that 
these numbers not only represent' the quantities of the different elements which 
unite with 8 parts of oxygen, tut they also indicate the simplest proportions in 
which tlie different elements can unite with each other. 

For example, not only does 1 part, by weight, of hydrogen, 1G of sulphur, 
28 of iron, and 100 of mercury, severally unite with 8 parts of oxygen, but 1 
part of hydrogen unites to form a compound with 16 parts of sulphur, and 16 
of sulphur in turn unites to form different compounds with 28 parts of iron and 
100 of mercury, or 39 of potassium. 

260. Law of Substitution .—It very often happens also, that through 
the varying force of affiinity, one element is able to expel and replace an- 
other in a compound previously formed. "When such a substitution takes 
place, it always happens in the quantities indicated by their proportional 
numbers. 

This principle may be illustrated as follows : — In mercantile transactions, 
100 dollars in money will purchase 6 ounces of gold, or 12 ounces of platinum, 
or 100 ounces of silver, or 1,500 ounces of mercury; consequently, 6 ounces of 
gold have the same commercial value as 12 ounces of platinum, or 100 ounces 
of silver, etc. The same principle holds good in chemistry: 28 ounces, or 28 
parts of any other denomination by weight, of iron, 100 of mercury, 108 of 
silver, or one of hydrogen, combine with 8 of oxygen. Accordingly 28 ounces 
of iron have same chemical value as 100 ounces of mercury, 108 of silver, or 
1 ounce of hydrogen. — Stockhardt. 

261. Chemical Equivalents. — The proportions, or 
quantities by weight, in which different substances unite 

Questions. — What remarkable fact has been ascertained respecting the proportion of 
the elements which combine with oxygen ? What are examples ? What is nnderstood 
by the law of substitutions ? How is this illustrated"? What is the meaning of chemical 
equivalents f 



166 INORGANIC CHEMISTRY. 

to form definite chemical compounds, are called Chemical 
Equivalents (from cequus, equal, and valor, value). They 
are also sometimes designated as combining, or equivalent 
weights. The numbers representing or expressing these 
proportions are termed equivalent numbers. 

Thus, by 1 equivalent cf oxygen is to be understood 8 parts of it by 
weight; by 1 equivalent of iron, 28 parts by weight; by 1 equivalent of mer- 
cury, 100 parts by weight. 

It will be readily observed that the numbers used to designate equivalents 
merely express the relative quantities of the substances they represent ; it is 
therefore a matter of little consequence what numbers are employed to ex- 
press them, provided the relations between them are strictly observed. Thus 
w r e may represent the equivalent of hydrogen (which is the smallest of all 
the equivalent numbers) by 100, or 1,000 as well as by 1, provided all the 
other equivalent numbers are multiplied in an equal ratio ; or hydrogen may 
be represented by .01 or .001, if all the other numbers are equally re- 
duced.* If hydrogen were represented by 100, oxygen would be 800, and 
iron 2,800. Or if hydrogen were 0*01, oxygen would be 0'08, and iron 0*28. 
It is the ratio, or relative proportion, which gives value to these numbers. 

In England and the United States, the combining number of hydrogen is 
made the unit of comparison. The reason why this element is selected is be- 
cause it combines with oxygen and other elements in a smaller proportion by 
weight than any other known substance, and the numbers representing the 
combining proportions of all the other elements, may also, with few excep- 
tions, and without material error, be taken as multiples by whole numbers of 
the equivalent of hydrogen. The equivalent number of hydrogen in this 
scale is 1, and as one part of hydrogen is united in water with exactly 8 
parts of oxygen, the equivalent number for oxygen is 8. 

On the Continent of Europe, most chemists make oxygen the unit of com- 
parison, and assume its equivalent number to be 100 : the equivalent number 
of hydrogen will be, therefore, 8 times less, or 12-5, and the equivalent num- 
bers of the other elements, calculated according to the hydrogen scale, will 
also be changed proportional^. 

In the following table the elementary substances are arranged alphabetically, 
with the symbols used by chemists to designate them affixed to each. The 
numbers representing their equivalent or combining proportions, calculated 
according to the hydrogen scale, are placed opposite to each element.* 



* The numbers on the hydrogen scale will be adopted in this -work, and, generally 
speaking, fractional quantities "will be omitted. 

Questions. — What of equivalent numbers? May the numbers expressing equivalents 
be varied and changed ? On what principle ? What is the unit of the scale adopted in 
England and the United States for indicating the numerical relations of the equivalents ? 
Why is hydrogen adopted ? What is the unit adopted upon the Continent of Europe ? 



PRINCIPLES OF CHEMICAL PHILOSOPHY. 167 

The names of the elements which from their rarity may be regarded as un- 
important, are given in Italics. 

TABLE OF THE ELEMENTARY SUBSTANCES, WITH THEIR EQUIVALENTS AND 
SYMBOLS. 



Aluminum 

Antimony (Stibium) 

Arsenic 

Barium 

3ismuth 

Boron 

Bromine 

Cadmium 

Calcium 

Carbon 

Cerium 

Chlorine 

Chromium , 

Cobalt 

Copper 

Didymium 

Erbium, 

Fluorine , 

Glucinium, , 

G-old (Aurum) 

Hydrogen 

llmenium 

Iodine 

Iridium 

Iron 

Lantanium , 

Lead (Plumbum) 

Lithium 

Magnesium , 

Manganese 

Mercury 



Symbol. H=l 



Al 

Sb 

As 

Ba 

Bi 

B 

Br 

Cd 

Ca 

C 

Ce 

CI 

Cr 

Co 

Cu 

D 

E 

r 

G 

Au 

H 

II 

I 

Ir 

Fe 

La 

Pb 

Li 

Mg 

Mn 

Hg 



13-7 
129- 

75- 

63-50 
312- 

10-0 

80- 

5o- 

20- 
6- 

47- 

35-50 

2U-7 

29-5 

31-7 



19- 
6-9 



127- 
99- 
28- 
3(3. 

10! 5 
6-9 
12-2 
27-6 

100- 



Nome. 



Molybdenum 

Nickel 

Niobium 

Nitrogen 

Osmium 

Oxygen 

Palladium 

Pelopium 

Phosphorus 

Platinum 

Potassium (Kalium) 

Rhodium 

Ruthenium 

Selenium 

Silicium, or Silicon 

Silver (Argentum) 

Sodium (Natrium) 

Strontium 

Sulphur. 

Tantalum (Columbium) 

Tellurium 

Terbium 

Thorium 

Tin (Stannum) 

Titanium 

Tungsten (Wolfram).. . . 

Uranium 

Vanadium 

Yttrium 

Zinc 

Zirconium 



Symbol. 


h=-i. 


Mo 


40- 


Ni 


29 -6 


Nb 




N 


14- 


Os 


99-6 


O 


8- 


Pd 


53-3 


Pe 




P 


32- 


Pt 


9S-7 


K 


39-2 


R 


52-2 


Ru 


52-2 


Se 


40- 


Si 


21-3 


Ag 


103- 


Na 


23- 


Sr 


44- 


S 


16- 


Ta 


92- 


Te 


64- 


Tb 




Th 


59 6 


Sn 


59- 


Ti 


25- 


W 


94- 


U 


60- 


V 


63-6 


Y 


32-2 


Zn 


32-5 


Zr 


22-4 



Three other substances discovered within the last few years, and desig- 
nated as Aridium, Donarium, and Norium, are claimed to possess an ele- 
mentary character. If their existence is fully established, the number of the 
elements must be considered as sixty-five. 

The law of equivalents applies to compound substances 
equally with the elements — -the equivalent of a combining 
number of a compound being always the sum of the 
equivalent of its components. 

Thus, since water is composed of 1 equivalent, or 8 parts of oxygen, and 1 
equivalent, or 1 part of hydrogen, its combinining proportion or equivalent is 
9. The equivalent of sulphuric acid is in like manner 40, because it is a com- 
pound of 1 equivalent, or 16 parts of sulphur, and 3 equivalents of oxygen; 
(3X8=24), and 16-f- 24=40. The equivalent number of potassium is 39, 



Question — Does the law of combination by fixed equivalents extend to union of com- 
pound substances? Illustrate this. 



168 INORGANIC CHEMISTRY. 

and as this element combines with 8 of oxygen to form potash, the equiva- 
lent of the latter must be 39-J-8— 47. Now, when these compounds unite, 
one equivalent of the one combines with one, two, three, or more equivalents 
of the other, precisely as the elementary substances do. For example, water 
unites with potash to form a compound, but it does so only in the proportion 
of 9 to 47 ; sulphuric acid also unites with potash to form a compound (sul- 
phate of potash), but only in the proportion of 40 to 47. 

To illustrate the advantage in practical operations of employing the scale 
of equivalents, we will suppose a person wishes to manufacture sulphate of 
potash, which is one of the ingredients which enter into the composition of 
alum. Having purchased in the market the necessary components of sulphate 
of potash, viz., sulphuric acid and potash, he mixes the two together, accord- 
ing to their equivalents, in the proportion of 40 parts (pounds, ounces, or 
tons) of sulphuric acid with 47 parts of potash. The result is. that all the 
sulphuric acid unites with all the potash, and the greatest product of the com- 
pound is obtained. If, on the other hand, he had mixed the sulphuric acid 
and the potash in any other than the above, or some multiple of the above 
proportions, there would have been an excess or deficiency of one of the 
ingredients, and consequently a loss of material. The sulphate of potash 
formed by the partial combination would also prove to be an imperfect article, 
from the mechanical mixture of the excess of one of the ingredients through- 
out its substance. 

Previous to the discovery of this law of equivalents, at about the com- 
mencement of the present century, it could only be ascertained by laborious 
trials, how much of one chemical substance was required to combine with, or 
replace another. It is now only necessary to refer to the table of the propor- 
tional, or equivalent numbers to ascertain beforehand the quantity to be em- 
ployed. 

262. Equivalent Volumes. — When bodies are capable 
of assuming the form of a gas, or vapor, and in this con- 
dition act chemically upon and combine with each other, 
a very simple ratio prevails between the quantities which 
enter into combination, measured merely by their bulk or 
volume. 

Thus, one volume of a gas, which may be distinguished as A, unites with 
one, two, or three volumes of B, or two of A may unite with three of B. 

If when two gases capable of union by contact are brought together, the 
volume of one is greater than its combining proportion, the 'excess remains 
uncombined. 

The volume of two gases, after combination, is often less than the sum of 



Questions Show in -what manner the law of equivalents is practically applied in chem- 
ical operations ? What is understood by equivalent volumes ? Does the volume of the 
gases always remain the same after combination? 



PKINCIPLES OF CHEMICAL PHILOSOPHY. 169 

of their volumes in their separate state ; or in other words, the two gases or 
vapors, by the act of union, sometimes experience a condensation. 

It is, however, a very curious fact, that when such a diminution of the 
volume occurs, it always takes place in a simple ratio to the volume of ono 
or both of the combining gases. Thus, three volumes of hydrogen and ono 
of nitrogen unite to form ammonia ; but when the union takes place, the four 
volumes instantly contract to two, or one half their former bulk. The weight, 
however, of the ammonia formed is equal to the united weight of the hydro- 
gen and nitrogen that have entered into its composition. 

263. Atomic Theory . — A consideration of the facts set forth, nat- 
urally suggests the inquiry, — Why is it that all the different kinds of matter 
with which we are acquainted, in entering into chemical combination with 
each other, are constrained to do so according to certain fixed weights and 
volumes, and not otherwise? The response from every thinking mind will 
unhesitatingly be that the phenomena in question must originate in accordance 
with some great law or principle in nature, so extensive and general in its 
character as to affect all matter. Experiment and observation do not, and 
probably can not, enable us to say definitely what this law is ; but a careful 
consideration and comparison of all the facts in the case, led Dr. John Dalton, 
an eminent English chemist, about the year 1808, to propose a theory which 
.so satisfactorily explains the remarkable . circumstances attending chemical 
combination, that scientific men of all countries receive it as substantially 
true. This theory is known as the "Atomic Theory," or the "Theory of 
Atoms." 

The atomic theory supposes, in the first instance, that 
all matter is composed of ultimate particles, or atoms, 
which are incapable of subdivision. (See § 4, page 10.) 

A belief in this hypothesis dates back to a very remote period. It was a 
doctrine taught by that sect of the Greek philosophers known as the Epicu- 
reans, and during the middle ages it formed a part of certain theological dog- 
mas maintained by parties in the church. In more modern times, it received 
the sanction of many men of high scientific attainment, as Newton, Bacon, 
and others.* These opinions can not, however, be regarded in any other 
light than as mere speculations, and it was not until laborious study and 



* "It seem3 to me," says Sir Isaac Newton, "that in the beginning, God formed mat- 
ter in a solid mass of hard, impenetrable particles ; and that these primitive particles 
being solids, are incomparably harder than any porous bodies compounded of them; so 
very hard as never to wear or break in pieces, no ordinary power being able to divide 
what God made one in the first creation." 



Qttestions. — What inquiry naturally arises in the mind from a consideration of the facts 
6tated ? According to what theory is chemical combination explained "? Who proposed this 
theory ? What does the atomic theory suppose in the first instance ? Is this supposition of 
recent origin ? 

P 



170 INORGANIC CHEMISTRY. 

research had elevated chemistry to the rank of an exact science, that anj 
rational evidence upon the subject could be appealed to. 

The atomic theory, as proposed by Dalton, further 
supposes, that the atoms of each separate elementary suta 
stance have all the same characteristic form and weight, 
and that when combination between two different ele^ 
ments takes place, one or more atoms of one substance 
arrange themselves in the most symmetrical manner pos- 
sible by the side of one or more atoms of another substance^ 
and thus form a compound atom. 

In the simplest combination, one atom of one substance combines with one 
atom of another, but in other instances the proportion may be as 1 to 2, 3, 4, 
and 5, or as 2 to 3, 5, T, eta One atom of one kind can not combine with 
one half an atom of a different kind, or with any other fractional part of an 
atom, for the reason that no such quantities exist — the atoms being incapable 
of division. Hence the immutable nature of all compound bodies existing 
either in nature or art. 

Furthermore, as combination of different substances takes place atom by 
atom, and as the atoms of each substance have a size and weight peculiar to 
themselves, we have an explanation of the circumstance that the chemicaJ 
union of quantities of different kinds of matter only occurs in unchanging pro- 
portions by weight and volume — for what is true of all the atoms of a mass, 
must be true of the whole. 

Again, a compound atom formed by the union of two dissimilar atoms, 
must, in uniting with other bodies, necessarily obey the same laws of com- 
bination as the elementary atoms, and be in turn incapable of division, since 
the very act of division would be its destruction, so far as its compound char- 
acter is concerned. 

A strong argument in favor of the truth of the atomic theory is, that no 
reasonable explanation of the facts pointed out can be given by the adoption 
of any other theory. If matter is infinitely divisible, and if atoms have no 
real existence, then there is no reason why bodies should not combine in all" 
proportions. One grain, ounce, or pound, of one substance ought to combine 
with the half, quarter, tenth, hundredth, and every other proportion of a 
grain, ounce, or pound, of some other substance, so as to form an infinite num- 
ber of compounds, all possessing different properties. But this, as has been 
already stated, never happens. 

Dr. Dalton was also the first who conceived clearly the idea, that from the 

Questions.— What does the atomic theory of Dalton further suppose ? How does tha 
immutable character of chemical compounds necessarily follow from the admission of 
these views? How is the doctrine of equivalent proportions explained by the atomio 
theory? What is a strong argument in favor of the atomic theory ? Can the relative 
weights of the ultimate atoms be inferred from the r^-xtiv . actuaJ weights of the ele- 
ments? 



PRINCIPLES OF CHEMICAL PHILOSOPHY. 171 

relative actual weights of the elements which make up the mass of any com- 
pound, the relative weights of the ultimate atoms themselves might be in- 
inferred, and represented numerically. The method of reasoning and deduc- 
tion by which this result is arrived at is as follows : — 

It is obvious that if we can, by any method, exactly fix the relative weights 
of the atoms of a few of the great elementary bodies, oxygen, hydrogen, 
nitrogen, carbon, etc., we can, by an extension of the process, solve the ques- 
tion for all other simple bodies, and for the most complex compounds into 
which they enter. Now, to attain this result, it is necessary to take one 
point as granted — the truth of which, although not susceptible of absolute de- 
monstration, is yet rendered probable by many concurrent facts. This once 
allowed, the process becomes one of simple inductive reasoning. It is 
assumed that when two elementary substances unite in several proportions 
to form different compounds, that the combination takes place in the first or 
simplest compound in the proportion of one atom of the one to one of the 
other ; in the second compound, of one atom to two atoms ; in the third, of 
one to three, and so on. 

Let us next examine the practical application of this supposition. "Water, 
composed of oxygen and hydrogen, is found to contain these ingredients in 
the proportion of 8 to 1 by weight. Assuming, which many reasons make 
probable, that it is their simplest form of union, viz., of atom to atom, we ob- 
tain at once the relative weight of the ultimate atoms of oxygen and hydro- 
gen — as 8 and 1 respectively. 

Again, we have a series of five chemical compounds of oxygen and nitro- 
gen, in which the proportion of oxygen increases uniformly in the ratio of the 
simple numbers, so that nitric acid, the fifth in order of these compounds, con- 
tains exactly five times the weight of that which exists in the protoxide of 
nit-ogen, the first of the series. Concluding that the latter is the simplest 
form, and consists of a single atom or combining proportion of each of its 
elements, we obtain, by analysis of this gas, the relative weights of 8 and 14 
for the atoms of oxygen and nitrogen composing it.* 

Here then we have already a short scale of proportions fixed ; in which 
hydrogen is the unit, oxygen 8, and nitrogen 14. The next step, in complet- 
ing the circle of combination, furnishes a test of the truth of these results. 
Ammonia is a compound of hydrogen and nitrogen; and its analysis, exactly 



* The student will perhaps be able to obtain a clearer idea of the relation of •weights 
and proportions existing in the five compounds of oxygen and nitrogen from the follow- 
ing table. 

RELATIVE WEIGHTS. RELATIVE PROPORTIONS. 

Nitrogen. Oxygen. Nitrogen. Oxygen. 

Protoxyd of nitrogen, 14 8 1 1 

Deutoxyd of nitrogen, 14 16 1 2 

Nitrous acid, 14 24 t 3 

Hyponitric acid, 14 32 1 4 

Nitric acid, 14 40 1 5 

Question. — How is this conclusion arrived at ? 



172 INORGANIC CHEMISTRY. 

made, gives proportions of the two which involve the same numbers as were 
obtained by the preceding methods. 

This test obviously becomes more stringent and complete as we extend the 
number of bodies thus brought into conjunctions, and find the relative weight, 
so determined for each, strictly maintained in all their forms of combination. 
The atomic weight of sulphur, for instance, is found, by analysis of its com- 
pounds with oxygen, to be 1 6. Examining its simplest form of union with 
hydrogen, in sulphuretted hydrogen, the proportion is found to be exactly 16 
to 1, or one atom of each, thus verifying the respective numbers before ob- 
tained. In a like manner all the other elementary bodies have been submit- 
ted, by experiment, to the same law, and have been found to furnish proofs 
precisely similar in kind. Thus the circle of demonstration has been contin- 
ually enlarged ; the evidence increasing in a geometrical ratio with the num- 
ber of objects brought within the scope of .inquiry. The conclusion is as cer- 
tain and complete as any one of pure mathematics ; or, if there be any excep- 
tions, they are only such as may be ascribed to imperfect examination, or 
some other cause not infringing on the truth of the fundamental principle. 

From what has been stated, it follows that the word 
atom may be used to express either an ultimate individual 
particle of a substance, or the simplest and smallest com- 
bining proportion of a substance. Indeed it is customary 
in chemical works to employ the word in both its signifi- 
cations — atom and atomic weights expressing the same 
thing as equivalent and equivalent weights. 

Many other curious facts and relations have been discovered since the first 
announcement by Dalton of the atomic theory, which present strong addi- 
tional evidence of the correctness of his views. 

264. Specific Heat of A to m s. — For example, there appears to be 
a relation between the atomic weight of a body and its capacity for heat. 
Thus, the atomic weights of the metals, iron, copper, mercury, and lead, are 
respectively represented by the numbers 28, 32, 100, 104. Now if any of 
these four metals be taken in these relative proportions, it will require the 
same expenditure of heat to make them equally hot. 104 pounds of lead can 
be heated up to 212°, for example, by burning the same amount of alcohol 
■which will heat 100 pounds of mercury, 32 of copper, or 28 of iron. A simi- 
lar correspondence is also known to exist between the atomic weights and 
the capacity for heat of tin, zinc, nickel, cobalt, gold, platinum, sulphur, and 
tellurium, and according to some authorities, the correspondence extends to 
all the elements. If this last supposition is true (which is not proved), the 
determination of the specific heat of a substance would also afford the means 
of knowing its atomic weight and combining equivalent. Compound atoms 

Questions. — Since the announcement of the atomic theory, have any circumstances con- 
firmatory of its correctness been discovered ? Is there a relation between the atomio 
weight of an element and its capacity for heat ? 



PRINCIPLES OF CHEMICAL PHILOSOPHY. 173 

have also, in some instances, been proved to have the same relations to heat 
as the simple atoms composing them. 

There has also an interesting relation been traced between the atomic 
weights, the specific gravities, and the combining measures or volumes of 
those elements which exist in the gaseous state, or are capable of assuming 
it. For example, a cubic foot of nitrogen weighs just 14 times as much as 
a cubic foot of hydrogen ; a cubic foot of chlorine 35 times as much ; of 
bromine, 80 times as much ; of oxygen, 16 times as much ; and the same 
measure of the vapor of iodine, 127 times as much. Now, these numbers re- 
spectively represent the density or specific gravity of these gases, compared 
with hydrogen as unity ; and they also represent the atomic weights, or com- 
bining equivalents, of these several elements, — with the exception of oxygen, 
which is double. 

It is important for the student, in the consideration of the whole subject, 
to clearly distinguish between the doctrine of chemical combination by 
equivalent?, or, as it is often termed, "by atomic weight," and the atomic 
theory. The first is a truth independent of all theory, and rendered manifest 
to our comprehension by experiment and practical demonstration. The 
atomic constitution of matter, on which the law of combination by propor- 
tions is supposed to depend, can not, on the other hand, be proved by ex- 
periment, and still remains, and probably ever must remain, in the condition 
of a highly probable theory. The most subtile and refined analysis has never 
yet enab'ecl any one to isolate an indivisible portion of matter, or even to 
adduce any direct evidence of the absolute existence of matter in this condi- 
tion.* 



* Experimental researches have, however, in some instances been made -with a view of 
obtaining information on this subject. Dr. Thompson, of England, from certain assumed, 
but probable data, estimated an atom of lead, which, according to the table of equiva- 
lents, is 104 times larger than an atom of hydrogen, as only 1-31 0,000,000,000th of a grain. 
Ehrenberg, the eminent microscopist, has proved that the size of atoms, if they exist, 
must be less than 1-6,000,000 of a line in diameter, a line being assumed as l-12th of an 
inch. More recently, Professor Faraday has endeavored, through the agency of light, to 
obtain some evidence of the existence of atoms. (See observations on divided gold, Lon- 
don Phil. Mag. , 1856-5T, also Annual of Scientific Discovery, 1857-53.) The only posi- 
tive result attained to was, to demonstrate that metallic gold, distributed mechanically 
throughout a liquid in particles so minute as to defy detection by the most powerful mi- 
croscope, still retained its general physical properties. 

Concerning the form of atoms two views are entertained. According to one hypothesis, 
atoms have the same form as the fragments obtained by splitting a crystallized body in 
the direction of its lines of cleavage. (See p. 55, § 73.) Antimony, which may be cleft in 
directions parallel to the faces of an acute rhombohedron, is resolved by this mode of di- 
vision into similar rhombohedrons of continually smaller and smaller dimensions ; and if 
we conceive the cleavage to be carried to the utmost possible limit, the smallest rhombo- 
hedrons thus obtained will be the atoms of antimony. Other substances, in like manner, 



Questions. — Is there any relation between the atomic weight, the specific gravity, and 
combining volume of certain elements ? What clear distinction should be made between 
the atomic theory and the law of equivalent proportions ? 



174 INORGANIC CHEMISTRY. 

265. Chemical Nomenclature and Symbols, — Chemists 
recognize three great classes of substances, viz., Acids, 
Bases, and Salts. 

Acids. — The common idea of an acid is, a substance so- 
luble in water, which possesses the property of sourness, 
and which exerts such an action on vegetable blue colors 
as to change them to red. The chemist, however, disre- 
gards these properties, and considers all those substances 
to be acids which enter into combination with bases to 
form salts. 

Yinegar, oil of vitriol or sulphuric acid, and aquafortis or nitric acid, are fa- 
miliar examples of the class of acids. 

Bases, — A substance which is capable of entering into 
combination with an acid, and by so doing destroys, or 
neutralizes its properties, is called a Base. The bases in- 
clude those substances known as the alkalies, beside many 
other bodies of entirely different character. 

Alkalies. — An alkali is a substance possessing many 
qualities exactly the reverse of those which belong to an 
acid. It dissolves in water, and produces a liquid, soapy 
to the touch. It has an acrid, nauseous taste, and restores 
the blue color to vegetable extracts which have been pre- 
viously reddened by acid. 

Potash, soda, and hartshorn or ammonia, are instances of well-known 
alkalies. 

Salts. — Any compound produced by the union of an acid 
and a base is termed a Salt. 

By the voltaic pile, salts are decomposed into acids and bases, the acids 
going to the positive pole, and the bases to the negative. "We, therefore, call 



admit of cleavage into cubes, prisms, etc. This view of the form of atoms offers the 
easiest explanation of the regular crystalline form, and the cleavage of simple substances. 
The second hypothesis supposes that atoms have a spherical form ; and that regular 
crystalline forms are occasioned by the peculiarity of their arrangement in varying num- 
bers and angles. Thus, 4 spheres forming a base, and 4 placed perpendicularly over 
them, may form a cube ; 2 or 4 layers of 3 each would give a prism, and so on. 

Questions. — What three great classes of substances are recognized by chemists ? What 
is an acid? What are examples of acids ? What are bases? Define an alkali. What 
are examples of alkalies ? What are salts ? In the decomposition of a salt by the voltaic 
pile, how do its constituents distribute themselves ? 



PRINCIPLES OF CHEMICAL PHILOSOPHY. 175 

the acid, in reference to its electrical character, the electro-negative constitu- 
ent of a salt, and the base the electro-positive. 

Some of the properties of acids and alkalies may be experimentally illus- 
trated by means of a colored vegetable solution, such as the purple liquid 
prepared by slicing a red cabbage and boiling it in water. If a quantity of 
this infusion be divided into two portions, and to the one be added a little 
weak sulphuric acid, a red liquid will be obtained. If to the other a solution 
of an alkali be added, as potash or soda, a liquid of a green color is formed. 
On gradually adding the alkaline solution to the other, stirring the mixture 
constantly, the green color of the portions first added instantly disappears, and 
the whole liquid remains red ; as more and more of the solution containing 
the alkali is added, the red by degrees passes into purple, and on continuing 
to add it, a point is reached when the original red liquid acquires a clear blue 
tint. At this moment there is neither free alkali nor free acicl in the liquid, for 
the two have chemically united with each other, and have lost their charac- 
teristic properties. If the solution be now evaporated at a gentle heat, a 
solid crystalline substance is obtained, resulting from the combination of the 
sulphuric acid with the potash. This substance is a salt, and is called sul- 
phate of potash.* 

The acids and the alkalies are both remarkable for their great chemical 
activity. The acids dissolve all the metals, even the most compact. They 
also, except when very weak, destroy the skin and nearly all animal and 
vegetable substances. The action of the alkalies, especially potash and soda, 
is no less marked. They destroy the skin, if allowed to remain on it, and 
gradually remove the glaze from vessels of glass and earthen-ware which 
contain them. They also quickly remove paint from the surface of any 
object upon which their solutions fall. But the most remarkable property of 
acids and alkalies, is the power which they have of uniting with each other, 
and destroying, or neutralizing the chemical activity which distinguishes them 
when separate. 

No simple or elementary substance has the properties of either an acid or 
alkali. Consequently, all acids and alkalies are compounds of two or more 
elements. 

266. Neutral Bodies, — A substance which possesses 
neither the properties of an acid nor a base, is termed 
neutral. 



* In practical chemistry, a blue substance, called "litmus," extracted from a species 
of lichen, is used extensively for determining the presence of an acid or alkali. Pape**, 
colored blue with the tincture of litmus, is instantly changed to red by contact with the 
most minute quantity of an acid in solution ; and the red color thus obtained is as quickly 
destroyed, and the original blue restored by the action of an alkali. Little strips of 
blue and red paper thus prepared, are kept constantly on hand in the laboratory, and 
are designated as "test papers." 

. Questions.— How may the properties of the acids and alkalies be illustrated ? What 
are the characteristic properties of acids and alkalies ? Does any simple substance possess 
the properties of an acid or alkali ? What are the neutral bodies ? 



176 INORGANIC CHEMISTRY. 

Water is the perfection of a neutral substance, although, in some instances, 
it may supply the place of an acid or a base. 

267. Origin of Chemical Nomenclature — The principles 
upon which chemical nomenclature is founded, were established by a com- 
mittee of the French Academy in 1787. It was found that owing to the 
rapid progress of science, the number of new chemical substances increased 
so fast, that unless some uniform system of naming and classifying were 
adopted, the most inextricable confusion would result. The committee, there- 
fore, devised a nomenclature which aims not merely to give a distinguishing 
name to the substances spoken of, but also to convey a knowledge of their 
components, and even of the proportions in which those components occur. 
This object was in a great degree attained to, and the system then instituted 
remains in use, so far as its essential features are concerned, to the present 
day. 

268. Nomenclature of the Elements , — The elements which 
have been known from the most remote period retain their common names, 
and also their Latin names, to a considerable extent — as for example, Iron 
(Ferrum), Gold (Aurum), Copper (Cuprum), Mercury (Hydragyrum), Silver 
(Argentum), Lead (Plumbum), Tin (Stannum). If the element has been made 
known in modern times through chemical research, the name it bears gener- 
ally indicates some distinguishing feature by which it is characterized : thus, 
Phosphorus (from the Greek 0wf, light, and <t>epo) to bring), from its property 
of shining in the dark; Chlorine (from x?„upoc, green), from its peculiar color; 
Bromine, from fiptiiiog, a stench, etc. To the recently discovered metals, a 
common termination in um has been assigned, as Platinum, Palladium, Iridium, 
Potassium, Sodium, Aluminum, etc 

269. Nomenclature of Compounds . — When two elements unite, 
the product is called a Unary compound (from bis, twice) ; thus, water, com- 
posed of oxygen and hydrogen, sulphuric acid, composed of oxygen and sul- 
phur, and oxyd of iron, composed of oxygen and iron, are examples of binary 
compounds. 

Compounds of binary combinations with each other, as sulphuric acid with 
oxyd of iron, are called ternary compounds (from ter, thrice), three elements 
being concerned. Most of the minerals are ternary compounds. 

Combinations of salts with each other are named quaternary compounds, 
or double salts. Alum is an example, being a compound of sulphate of pot- 
ash and sulphate of aluminum. 

Compounds of oxygen are termed oxyds. Thus water 
is an oxyd of hydrogen, iron-rust an oxyd of iron. 

The binary compounds of chlorine, bromine, iodine, fluorine, and several 
other elements which resemble oxygen in their mode of combination, are 

Questions. — What was the origin of the chemical nomenclature now in use ? What is 
the general nomenclature of the elements? What are binary compounds? What are 
examples? What are ternary compounds? Give examples. What are quaternary 
compounds? What are examples? What are compounds of oxygen called? What the 
compounds of chlorine, iodine, fluorine, etc ? 



PRINCIPLES OF CHEMICAL PHILOSOPHY. 177 

distinguished by the final termination ide. Thus chlorine forms chlorides ; 
iodine, iodides; fluorine, fluorides; sulphur, sulphides, etc.* 

"When oxygen combines with the same element in more than one propor- 
tion, forming different oxyds, the several combinations are distinguished from 
each other by the use of prefixes. Thus, the first oxyd, or the one which 
contains but one equivalent of oxygen, is known as the Protoxide (from the 
Greek irpurog, the first) ; the compound of two proportions is, in like manner, 
designated as the deutoxyd (devrepor, double), and also as the binoxyd ((3i, 
double) ; the compound of three proportions is also known as the tritoxyd 
(Tptror, third). 

The oxyd, also, which contains the largest proportion of oxygen with 
which the body is known to unite, is termed the peroxyd. In like manner, 
the highest combinations of chlorine, sulphur, iodine, etc., are termed per- 
chlorides, persulphides, periodides. 

For example, oxygen unites with hydrogen in two proportions : the first 
combination is the protoxyd of hydrogen (water) ; the second and highest 
is the peroxyd. Again, with manganese, oxygen unites in three propor- 
tions : the first is termed the protoxyd, the second the deutoxyd, or binoxyd, 
and the third the peroxyd. 

With some elements oxygen enters into combination in the proportion 
of 3 to 2, or in the ratio of 1£ of oxygen to 1 of the element. Such a com- 
pound is termed a sesquioxyd (from the numeral sesqui, once and a half). 
Certain other oxygen compounds are formed in the proportion of 2 of tho 
element to 1 of oxygen; such are termed suboxyds, as the suboxyd of 
copper. 

When the compounds formed by the union of oxygen with the different 
elements possess an acid character (as very many of them often do), a different 
plan is adopted to mark this peculiarity. The compound is then termed an 
acid, and its name is derived from the substance which combines with the 
oxygen, with the termination ic added. Thus, sulphur with oxygen gives sul- 
phuric acid ; carbon with oxygen, carbonic acid ; and phosphorus with oxygen, 
phosphoric acid. It frequently happens, however, that an element forms 
more than one acid with oxygen. When this is the case, the termination ic 
is applied to the strongest acid, and ous to the weaker. Thus we have sulphuric 
and sulphurous acids, nitric and nitrous acids. 

The salts which these and other similar acids form by uniting with bases, 
are named in an equally simple manner, the acid supplying the generic, and 
the base the specific name : the ous termination of the acid is also changed 
into ite, and ic termination into ate. Thus, sulphite of soda, nitrite of potassa, 



* Binary compounds of sulphur, phosphorus and carbon, are also very generally known 
by the termination uret, as sulphuret of iron, carburetted hydrogen, etc. 

Questions. — How are the first, second and third oxyds distinguished? What is a per- 
oxyd ? What is a protoxyd? What is a perchloride ? What is a binoxyd ? What are 
eesquioxyds ? What are suboxyds ? How are acid compounds of oxygen named ? 



178 INORGANIC CHEMISTRY. 

sulphate of soda, and nitrate of potassa, are salts respectively of sulphurous, 
nitrous, sulphuric and nitric acids.* 

This nomenclature served to distinguish these acids and their salts until, as 
the science of chemistry advanced, a compound of oxygen and sulphur was 
discovered containing less oxygen than the sulphurous, and then a new name 
was required ; it was therefore called hyposulphurous acid, and the salt formed 
with it is termed a hyposulphite (from the Greek vtto, under) ; so also, when 
an acid was discovered containing less oxygen than the sulphuric, but more 
than the sulphurous, it was called hyposulphuric, and its salt a hyposulphate. 
In some cases acids have been discovered containing more oxygen than those 
already named with terminations in ic ; to these the prefix hyper (from the 
Greek v 71-ty, over) is attached. Thus chloric acid was for a very long time 
the highest oxygen compound with chlorine, but another still higher is now 
known. The last, therefore, is designated as hyperchloric, and sometimes as 
perchloric acid. Its salts are called hyperchlorates. 

270. Classification of Acids . — It was once supposed that the pres- 
ence of oxygen in a substance was essential to its acidity, but the progress of 
research has revealed the existence of acids which are entirely wanting in 
oxygen. Most of the acids which are wanting in oxygen contain hydrogen 
in its place. They are distinguished by prefixing to them the word hydro, 
as an abbreviation for hydrogen. Thus, chlorine and hydrogen form an acid, 
hydrochloric acid, often called muriatic acid ; cyanogen and hydrogen form 
hydrocyanic acid, or prussic acid ; sulphur and lrydrogen form hydro sulphuric 
acfd, etcf Some chemists, especially the French, transpose these terms; 
they speak of chlorohydric, acid cyanhydric acid, sulphydric acid, etc. There 
is an advantage in this alteration, as it avoids any ambiguity which might 
arise from the use of the prefix hydro, which has sometimes been applied to 
compounds which contain water. 

2*7 1. Classification of Salts . — In the early days of chemistry, 
the term salt was applied to all substances indifferently, which resembled com- 
mon salt in appearance and properties. Subsequently, the use of the term 
was restricted to those compounds only which were formed by the union of 
an acid and a base : but when chemical knowledge had still further progressed, 



* It may here be -well to caution those who are just commencing the study of chemistry, 
of the necessity of distinguishing clearly between compounds such as the sulphites and 
the sulphates, or the sulphides and the sulphites. Sulphide of sodium is a binary com- 
pound of two elementary bodies, sodium and sulphur ; sulphite of soda is a more complex 
compound, formed by the union of sulphurous acid and the oxyd of sodium (soda) ; sul- 
phate of soda is formed by the union of sulphuric acid and soda. 

t The acids formed by the union of sulphur and arsenic with hydrogen are also very 
commonly known as sulphuretted hydrogen, and arseniuretted hydrogen. 

Questions. — How are the different acid compounds distinguished ? How are salts 
named ? What gives the generic and what the specific name to a salt ? How do acids in 
forming salts change their terminations ic and ous ? What do the prefixes hypo and 
hyper designate ? Is the presence of oxygen essential to the existence of an acid ? What 
element generally supplies the place of oxygen in acids wanting this element ? How are 
hydrogen acids named ? 



PRINCIPLES OF CHEMICAL PHILOSOPHY. 179 

it was found that if this definition was rigidly enforced, it would exclude from 
the class of salts a considerable number of compounds which possess the 
physical characteristics of a salt in a most eminent degree. Among these 
was common salt itself, which, although the type of all salts, is not a com- 
pound of an acid or a base, but a compound of two elements, chlorine and 
sodium. In like manner, the compounds of iodine, bromine, and fluorine 
with the metals, possess in a very high degree the saline character. To ob- 
viate, therefore, the somewhat startling proposition, that common salt is no 
salt at all, and to avoid doing violence to a long- received and expressed com- 
mon idea, two classes of salts were established. 

The first class includes all those binary compounds which, like common 
salt, are formed by the direct union of a metal with some other substance, 
called a salt radical, as chlorine, fluorine, bromine, etc. Compounds of this 
character are termed Haloid Salts. 

Radical . — The term radical in chemist^, is generally applied to any 
substance, simple or compound, which can unite with hydrogen to form an 
asid compound, and with a metal to form a salt. 

The second class includes all those salts formed by the union of an acid 
and a base.* These are termed oxy-salts, or oxygen acid salts. 

Many of the compounds of sulphur with the metals, as the compound of 
sulphur and potassium, also possess a saline character, and are termed sul- 
phur salts. 

Such in general are the principles of chemical nomenclature, as established 
by the Committee of the French Academy. As before said, the object of the 
inventors of this language was not only to give a distinguishing name to the 
substances spoken of, but also to convey a knowledge of its chemical compo- 
sition. That this has been accomplished in a great degree, will be evident 
from one or two illustrations. Thus, the name bi-chromate of potash indicates 
by simple inspection that the substance is an oxygen acid salt, composed of 
chromic acid and potash, the prefix hi showing that the equivalent or pro- 
portion of acid to base is as two to ore. Again, the name permanganate of 
'potash indicates a compound of manganic acid and potash, and the prefix per 
shows that the acid in question is the highest oxygen compound of mangan- 
ese known. 

212. Symbols. — Although the chemical nomenclature in use is most 
convenient, and perhaps as perfect in principle as the nature of our language 



* A beautiful illustration of the universality of the law, that bodies replace each other 
<a combination in fixed equivalent quantities, is found in the combination of salts. Thus, 
tfhen equivalents of two neutral snlts, which are capable of decomposing each other, are 
brought into chemical contact with each other, the two bases exchange acids by an exact 
compensation ; the original compounds are altogether lost, and two new salts evolved, 
without either loss or addition of any kind in the process. 

Questions. — What two classes of salts have been recognized in chemistry? What are 
haloid salts ? What are oxysalts ? What are sulphur salts ? Illustrate by example the 
manner in which the chemical name of a substance indicates its composition. What is 
the necessity of using symbols in chemistry?, 






180 INORGANIC CHEMISTRY. 

will allow, yet the impracticability, in many cases, of contriving convenient 
names expressive of the constitution of many complex chemical compounds 
(the existence of some of which was not known or even anticipated by the 
inventors of chemical language), has led to the employment of symbols. 
These constitute a species of short-hand, which not only supplies all de- 
ficiencies of the nomenclature, but enables us to represent to the eye, and 
describe with mathematical accuracy and rapidity the known composition of 
every chemical substance, and the changes which it may undergo. The em- 
ployment of symbols has now become universal, and is also indispensable to 
both teacher and student in the study of chemistry. 

273. Symbols ofElements — It has been agreed by all 
chemists to use, as symbols of the elements, the first let- 
ter of their Latin names. When two or more names com- 
mence with the same initial, a second distinguishing letter 
is added. 

In the table of elementary bodies, the symbol of the several elements will 
be found opposite to their names. 

The symbols, when used singly, represent not merely the element for which 
they stand, but one equivalent of that element. Thus, the symbol stands 
not for oxygen in general, but for one equivalent of oxygen, or, hydrogen 
being unity, for the number 8. H, in like manner, stands for one equivalent 
of hydrogen, and the number 1 ; C for one equivalent of carbon, and the 
number 6 ; Pb for one equivalent of lead, and the number 104. 

If more than one equivalent of a body has to be expressed, it is signified 
either by writing a small figure to the right of the symbol, and generally be- 
low the fine. Thus — 

O2 stands for 2 equivalents, or 16 of oxygen. 
O5 " 5 " or 40 

The same may be represented also by prefixing the number to the symbol, 
as 20, 50. 

The symbol may also be considered as representing the atomic constitution 
of a body. For example, O stands for one atom of oxygen as well as for 
one equivalent ; O2 for two atoms ; Os for five atoms. 

274. Symbols of Compounds.— In order to form the 
symbol of a compound, we unite the symbols of the ele- 
ments of which it consists, one after the other, indicating 
by means of figures the number of each which have en- 
tered into combination. 

Thus, 110 is the symbol of water, a compound consisting of one equivalent, 
or 1 of hydrogen, and of one equivalent, or 8 of oxygen ; SO3 is the symbol 

Questions. — What symbols are used to designate the elements ? What does a single 
symbol of an element represent '? How are several equivalents of an element represented 
by symbols ? How is the constitution of compounds represented by symbols ? 



PRINCIPLES OF CHEMICAL PHILOSOPHY. 181 

of sulphuric acid, a compound consisting of one equivalent, or 16 of sulphur, 
and three equivalents, or 24 of oxygen. Cm H n On is the symbol of com- 
mon sugar, a compound consisting of twelve equivalents of carbon, eleven 
equivalents of hydrogen, and eleven equivalents of oxygen. 

A collection of symbols indicating the constitution of compounds, is caUed 
a formula. 

Compounds united with compounds, such as salts, are expressed in a simi- 
lar manner, the base of the salt, or the electro-positive element, being always 
placed first. Thus, sulphuric acid has the formula SO3, and oxyd of iron, 
that of FeO, consequently the formula FeO-f-S03 will represent one equiva- 
lent of sulphate of the protoxyd of iron. Frequently a comma is placed be- 
tween the two compounds instead of the algebraic sign -f. Thus, sulphate 
of iron may be written FeO, SO3. This mode is usually adopted to express 
a more intimate union than when the sign -f- is used. Thus, SO3, HO,-(-2 HO 
indicates that an equivalent, or compound atom of sulphuric acid has united 
with three equivalents of water, two of which are loosely retained, and one 
very strongly."- 

"Where it is necessary to indicate more than one equivalent of a compound, 
the whole formula of that compound is included in a bracket, and preceded 
by the indicating number. Thus, three equivalents of sulphate of iron would 
be written 3 [FeO, SO3]. The figure prefixed multiplies nothing beyond 
the symbols included within the bracket. Thus, in the formula for crystal- 
lized alum — 

Al 2 3; 3[S0 3 ]+KO, S0 3 +24 HO, 
the 3 which precedes S O3 only indicates that three equivalents of sulphuric 
acid are present. Frequently the employment of brackets is neglected, and 
then the figures multiply all the symbols included between them and the next 
comma or sign of addition. 

275. Reactions and Reagents.— The various chemical 
changes, to which all matter is more or less liahle, are 
termed, in the language of chemistry, reactions and the 
agents which cause these changes, reagents. 

In addition to the information which symbols convey relative to the com- 
position of the substances for which they stand, they can also be so combined 
in the form of equations, as to show in the most perfect manner the various 
products which result from chemical reactions. For this purpose, the symbols 
of the substances involved in the reactions are placed together, so as to form 
one side of the equation, and the symbols of the products resulting from the 
reactions on the other side. But as not the smallest particle of matter can be 
annihilated by any chemical action, it follows that the value of both sides of 



Questions. — What are chemical formulae? How is the composition of salts indicated 
by symbols ? Which constituent of a salt is placed first ? What does the sign + mean ? 
What is to be understood by the terms reactions and reagents ? How may symbols be 
arranged so as to indicate chemical reactions and their products ? 



182 INORGANIC CHEMISTRY. 

the equation must be equal, or in other words, the sum of the weights of the 
products of every reaction must be always equal to the sum of the weights 
of the substances involved in the change. For example, the decomposition 
of carbonate of lime (marble) by sulphuric acid, and the liberation of carbonic 
acid gas may be represented by the following equation : 

20-f8,-f6+16,-fl6- r -24=20-i-8,+16-|-24-h64-lG==90. 
Ca 0, C 2 + S Os=Ca 0, S 3 +C 2 . 
The correctness cf this equation may be proved by adding together the 
equivalents of both sides, when the sums will be found to be equal. 

A very little practice will render the use of symbols familiar to all. To 
expedite the acquisition of this knowledge, the student will find it advan- 
tageous to exercise himself in the expression of chemical changes by sym- 
bols, whenever the opportunity occurs, until he is thoroughly acquainted with 
their signification and use. 

276. Isomerism . — Until within a recent period, it was an acknowledged 
principle, that two bodies containing the same elements combined in exactly 
the same proportion, must of necessity possess the same properties, and be 
mutually convertible into each other. Such, however, is not the fact, and 
numerous substances are now known to exist, which are identical in chemical 
composition and yet exhibit totally distinct physical and chemical properties. 
Different bodies thus agreeing in composition but differing in properties, are 
said to be isomeric (from iooe, equal, and fiepog, part), and the phenomenon in 
general is termed Isomerism. 

A great class of bodies known as the volatile oils, oil of turpentine, oil of 
rosemary, oil of lemons, and many others, are examples of bodies which dif- 
fer widely from each other in respect to odor, medicinal effects, boiling point, 
specific gravity, etc., and yet are exactly identical in composition — that is, 
they contain the same elements, carbon and hydrogen, in the same propor- 
tions.* " The crystallized part of the oil of roses, the delicious fragrance 
of which is so well known, a solid at ordinary temperatures, although read ly 
volatile, is a compound body containing exactly the same elements, and in 
the same proportion, as the gas we employ for lighting our streets." 

The difference of properties in isomeric bodies is explained very simply by 
the atomic theory. " It is supposed that the atoms in each particular case 
are differently arranged, in the same way as the most manifold grouping may 
be produced on a chess-board by transposition of the white and black squares, 
as is shown in Fig. 76. Each figure is composed of eight white and eight 
black squares, but though the absolute number is the same, the grouping is 
different. In a one and one, in b two and two, in c and d lour and four 



* Two conditions of isomerism may be noted ; one in which tho absolute number of 
atoms, and consequently the atomic weight of the compound, is the same; the other 
where, though the relative proportions of the elements are the same, the absolute num- 
ber of atoms of each is different. 

Questiox6. — Illustrate this by example. What is isomerism? Give examples of 
isomeric bodies. How is isomerism explained ? 



PRINCIPLES OF CHEMICAL PHILOSOPHY. 1S3 

squares arc so joined as to present a different appearance. If we imagine 
these squares to be atoms, we obtain an idea of isomeric bodies, and it is thus 
rendered clear how there may be bodies of the same constitution and form, 

Fig. 76. 







yet presenting an entirely different appearance and possessing different prop- 
erties." — Stockhardt. 

277. Allot ropism . — Many of the elements are capable of existing in 
two or more different conditions, or forms, in each of which they manifest 
different, and often opposite properties. This principle is termed Allotropism, 
and bodies manifesting changes of such character are called Allotropic (from 
dJJiOTpoTcoq, different nature). 

One of the most striking illustrations of allotropism is to be found in the 
case of the element carbon, which exists in a pure state in the brilliant trans- 
parent diamond, in the opaque and black charcoal, and in the metallic-like 
body known as graphite, or black-lead. • Sulphur, phosphorus, silicon, boron, 
oxygen, and other elements, are susceptible of similar changes. 

Bodies in allotropic conditions differ in their chemical as well as in their 
physical properties. Carbon as the diamond is almost incombustible ; carbon 
as lamp-black inflames at a low temperature, and sometimes ignites sponta- 
neously. Phosphorus, in the ordinary condition, is soft, yellowish in color, 
has a powerful smell and taste, and can scarcely be handled with impunity, 
since it bursts into a flame at a temperature a little above that of the human 
body ; allotropic phosphorus, on the contrary, is of a dark color, hard, de- 
void of both smell and taste, and may be handled without danger, and be 
even carried in one's pocket. 

The explanation of allotropism is referred to difference in the arrangement 
of the particles or atoms constituting the body. Thus the same fibres of cot- 
ton, when closely matted together, constitute hard, tough paper ; when simply 
carded, wadding ; when twisted, yarn, or thread ; and when intertwined, cloth. 

Questions. — What is allotropism ? What are examples of allotropism ? How is this -y*" 
condition explained? 



184 INORGANIC CHEMISTRY. 

CHAPTER VI. . f 

THE NON- METALLIC ELEMENTS. 

278. The generally recognized division of the simple substances into Metal- 
lic and Non-metallic elements, or the Metals and Metalloids, (from juera/.Xov, 
metal, and eidoc, appearance,) although most convenient for description, is 
not established in nature, and no strict line of separation, moreover, between 
the two classes can be indicated, since some of the elements possess, in a 
nearly equal degree, the characteristics of both. 

Metalloids. — The number of the elements generally 
included in the class of metalloids is fourteen, which 
may be enumerated as follows : — Oxygen, Hydrogen, 
Nitrogen, Chlorine, Iodine, Bromine, Fluorine, Sulphur, 
Selenium, Tellurium, Phosphorus, Silicon, Boron, and 
Carbon. 

Characteristics of the Metalloids . — The characteristics 
which serve in general to distinguish the metalloids from the metals are 
as follows: — They do not possess a metallic appearance, and are bad con- 
ductors of heat and electricity. When binary compounds of the metals and 
metalloids arc decomposed by the agency of galvanism, the metalloids always 
separate at the positive pole (copper side), and the metals at the negative 
pole; as bodies endowed with opposite electricities only are attracted, the 
metalloids are, for this reason, termed electro-negative elements, and the 
metals electro- positive elements. Almost all the metalloids combine with 
hydrogen, but, as a general rule, the metals do not. 

SECTION I. 

OIT GEN. 

Equivalent 8. Symbol 0. Density l'l. (Air—1.) 

279. II i s t o r y. — Oxygen gas was discovered by Dr. Priest- 
ley, an English clergyman, in 1774. He called it depho- 
gisticated air. 

In the following year it was again discovered by Scheele, a Swedish chemist, 
and by Lavoisier, the illustrious French chemist, without cognizance of Priest- 
ley's discovery. The latter, supposing it to be the sole agent which imparted 
to bodies their acid properties, gave it its present name, oxygen, (from o£vg, 
acid, and yevaw, I give rise to). 

Questions. — How are the elements divided ? Is this division founded in nature ? How 
many of the elements are generally included among the metalloids? Name them. What 
are the characteristics of the metalloids ? When and by whom was oxygen discovered ? 
From whom did oxygen derive its name ? 



r 



OXYGEN. 



1S5 



280. Natural History and Distribution. — Oxygen is the 
most abundant of all the elementary substances, but is never met with in na- 
ture in a pure or isolated conditiou. It constitutes at least one tMrcTpart of 
the solid crust of the globe, eight-ninths by weight of all the water upon its 
surface, more than one fifth of the atmosphere, and eight-ninths of the vapor 
contained in the atmosphere. It is also an essential constituent of all living 
structures, and is the immediate agent by which animal life and all the pro- 
cesses of combustion are sustained. 

The meteoric masses which fall to the earth from the inter planetary spaces, 
have little or no oxygen in their composition, and in this respect they are 
unlike any of the compound substances which compose the crust of the globe. 
Hence the inference has been drawn, that in some of the great planetary masses 
of the solar system, from whence meteorites are undoubtedly derived, oxygen 
does not exist at all, or in much smaller proportions than upon the earth. 

281. Preparation. — Many solid substances, which con- 
tain oxygen in combination, readily evolve it in a gaseous 
form when subjected to a sufficiently high temperature. 

A very easy method of obtaining a small quantity of oxy- 
gen gas for experiment, which at the same time illustrates the 
original process by which Priestley discovered it, is to heat 
a little of the red oxyd of mercury in a thin glass tube (Fig. 
11) over a spirit-lamp.* In this substance the affinity, or 
chemical attraction which holds together the mercury and 
the oxygen is so feeble, that a very slight degree of heat 
suffices to bring about decomposition ; — the mercury collecting 
in small globules on the bottom and sides of the tube, and 
the oxygen escaping as a gas. The presence of the latter J 
element may be demonstrated by holding an ignited sub- 
stance over the mouth of the tube. 

If it is desired to collect and preserve the oxygen liberated 
in this experiment, one end of a bent glass tubef is fitted by means of a per- 

* Cylindrical glass tubes, with rounded bot- 
toms, known as " test tubes," are generally used 
in chemical experimentation. A simple wooden 
rack, as in Fig. 78, serves as a convenient stand 
for them. Teachers will do well to furnish 
themselves with a supply of these tubes, as they 
are inexpensive, and can be used for a great va- 
riety of purposes. 

t Glass tubing prepared expressly for chemical 
m \':ipulations can be procured at a small expense 
of any dealer in chemical apparatus. By means 
of a Berzelius spirit-lamp, and with a little prac- 
tice, an inexperienced person can, in a short time, learn to bend and adapt his tubing 
to his apparatus with ease and rapidity. 

Questions. — What is said of the importance and distribution of oxygen? What infer- 
ence has been drawn from the composition of meteoric stones ? How is oxygen generally 
procured ? By what simple method may a small quantity of oxygen be obtained ? 





186 



INORGANIC CHEMISTRY. 



forated cork into the mouth of the generating tube, and the other end is con- 
ducted into a vessel filled with water. The apparatus thus arranged may be 
^ ,_ supported by means of a piece 

of cord or wire, or by a sort of 
wooden vice (retort holder) con- 
structed for chemical purposes, 
and represented in Pig. 79. The 
oxygen escaping in bubbles from 
the end of the tube under water 
is collected in a glass bottle or 
jar, which has been previously 
filled with water and inverted 
in the vessel ; care being taken 
either to close the mouth of the 
jar, or else keep it continuously 
under water during the act of 
inversion. No water will escape 
from the jar until bubbles of gas 
from the tube are passed into it ; 
but when this is permitted, the 
gas, by reason of its superior levity, ascends and displaces the water. As 
soon as one jar is filled it may be removed, and its mouth closed with a cork, 
or kept below the water level, and another substituted in its place. (See 
Fig. 79.) 

For the production of oxygen gas in considerable quantity, materials less 
expensive than the red oxyd of mercury are used. The most convenient, and 
under ordinary circumstances the most economical method which can be 
adopted is, to expose to heat in a retort, or flask furnished with a bent tube, 
a perfectly dry mixture of equal parts of chlorate of potash and black oxyd 
of manganese. A common Florence flask will serve for this purpose, but a 
flask constructed of sheet copper and fitted with a small lead tube and screw- 
cap, is preferable.* A spirit-lamp affords sufficient heat to effect the chem- 
ical decomposition, and the gas liberated is collected in the manner before 
described. The salt chlorate of potash is very rich in oxygen — every 124 
parts of it by weight containing 48 parts of this element united in the solid 
form with 36 parts of chlorine and 39 of the metal potassium. On the appli- 




* Flasks, or generating bottles constructed of thin sheet copper, and furnished ■with a 
small leaden tube and a screw-cap, may be purchased of dealers in chemical apparatus, or 
can be easily manufactured by a coppersmith. For a continuous course of experiments 
their employment is strongly recommended, as they obviate entirely the annoyance and 
trouble arising from the fracture of glass, and the adjustment and preparation of tho 
tubes. 



Questions. — What is the most convenient and economical method of obtaining oxygen 
in moderate, quantities ? Describe the method of obtaining oxygen from chlorate of pot- 
ash? 



OXYGEN 



187 



cation of heat, all this oxygen is driven off in a gaseous state, and chlorine, 
united with potassium, forming the chloride of potassium, remains. The re- 
action may be represented as follows : — 

35 + 40 + 39 + 8=35 + 39 + 48=122 
CI 05 K O=01 K + Oo. 

Chlorate of potash and black oxyd of manganese both yield oxygen when 
heated separately, but under the conditions of heat and mixture above speci- 
fied, the chlorate of potash alone disengages oxygen. The manganese, how- 
ever, without taking any part in the chemical decomposition, exercises an 
important influence on the process, apparently by its mere presence, causing 
the oxygen to be liberated with the utmost facility and regularhy, and at a 
much lower temperature than when the chlorate is used alone. The action 
of the manganese in producing this effect has been explained, by suppos- 
ing that it mechanically separates the particles of the salt, and thus dis- 
tributes the heat uniformly ; but if this is true, clean sand, powdered glass, 
or any other similar material, ought to act equally well, which is not the 
case. 

"When very large quantities of 
oxygen are required, and perfect 
purity of product is not essential, an 
economical plan is generally adopt- 
ed of heating the black, or peroxyd 
of manganese to redness in an iron 
retort, arranged in a suitable fur- 
nace. (See Fig. 80.) One pound 
of good oxyd of manganese thus 
heated, will yield seven gaUons of 

oxygen, with some carbonic acid. This last may be entirely removed by 
causing the gas to pass through a solution of potash. In this process MnO s 
becomes converted in MnO-j-0. 

Oxygen may be obtained from various other substances, but those already 
mentioned are the best, and the most frequently employed.* Red lead (oxyd 
of lead), and likewise saltpetre, when heated strongly, will furnish this 




* A new method of preparing oxygen on an extensive scale for economic purposes, has 
recently been proposed by M. Boussingault. He states that caustic baryta, when heated to 
a particular temperature in the free presence of air, absorbs oxygen, and becomes per- 
oxyd of barium, but on increasing the heat, the oxygen absorbed is given up. Thus the 
same quantity of baryta may be made to alternately absorb oxygen and evolve it into a 
reservoir. 



Questions. — How much oxygen does this substance contain ? "What is the chemical 
reaction in this process? What is the object of mixing manganese with chlorate of pot- 
ash ? Is the action of the manganese understood ? When large quantities of oxygen are 
required, what method is adopted ? What is the chemical reaction in this process ? From 
what other sources may oxygen be obtained ? 



188 INORGANIC CHEMISTRY. 

gas. A mixture of strong sulphuric acid and one half its weight of black 
oxyd of manganese, or bichromate of potash, will liberate oxygen when 
heated. 

All the green parts of plants evolve oxygen when exposed to the light of 
the sun. This fact may be readily demonstrated by placing a leafy branch, 
which is still connected with the parent plant, or a number of fresh leaves, 
under ajar filled with water, and then exposing them to the influence of 
solar light. After a short time small air-bubbles, consisting of pure oxygen, 
will collect in the upper part of the vessel. The minute bubbles, also, which 
may be often seen adhering to the leaves of aquatic plants under water, are 
generally pure oxygen. 

282. Properties of Oxygen . — Oxygen, when pure, can not be 
distinguished from atmospheric air, being colorless, tasteless, and, under or- 
dinary circumstances, destitute of odor. It is, however, somewhat heavier 
than atmospheric air; the dersity of the latter being represented by 1*00, 
that of oxygen would be 1-10. 

One hundred cubic inches of dry oxygen weigh 34-20 grains. In its sepa- 
rate condition it is known only as a gas, all attempts to reduce it, by im- 
mense pressure and extreme low temperature acting conjointly, into a solid, 
or even liquid condition, having failed. Yet the learner will not fail to per- 
ceive, that oxygen when locked up in combination with the solid substances 
from whence we obtain it, must be itself a solid ; and this consideration en- 
ables us to form some conception of the enormous force which, under the 
name of affinity, is capable of producing this effect. 

Oxygen is very slightly soluble in water ; a hundred volumes of this fluid, 
at ordinary temperatures, dissolving only four and one half volumes of the 
gas. Oxygen possesses a wider range of affinities than any other known 
substance, and combines in one or more proportions with all the elements 
except fluorine. The act of union of a substance with oxygen is termed 
oxydation, and the product of the union is called an oxyd. Oxyds are classi- 
fied and divided, as has been before shown (§ 265), into acids, bases, alkalies, 
etc. 

The tendency of oxygen to unite with other substances varies according to 
the circumstances under which the latter are presented to it, being greater 
under the influence of heat than of cold, and greater where there is an ex- 
cess than where there is a deficiency of oxygen. Oxygen, at ordinary 
temperatures, enters slowly into combination with most of the metals. This 
action takes place much more rapidly in a moist than in a dry atmosphere. 
A bar of polished iron, in perfectly dry air at the ordinary temperature, will 

Questions.— Do plants evolve oxygen ? What experiment proves this ? What are the 
properties of oxygen ? Has oxygen ever been condensed into a liquid or solid substance ? 
Is it known to exist in either of the latter conditions? Wbat is said of its solubility in 
water? Of its range of affinity? What are the products of the union of oxygen with 
other substances called ? How does the tendency of oxygen to unite with other sub- 
stances vary ? What is said of the oxydation of the metals ? Will iron rust in dry air at 
ordinary temperatures? 



OXYGEN. 189 

remain unchanged for any length of time, but if moisture be present, it 
quickly becomes rusty. In the case of iron, the oxydation once commenced 
will spread through the entire mass of the metal ; but in other instances, as» 
in the case of lead and zinc, a superficial coat of the oxyd is formed, which 
adheres firmly to the surface, and protects the metal beneath from further 
change. 

In order to commence and carry on oxydation, it is generally necessary to 
apply heat. An iron bar, when heated red hot, and exposed to the oxygen 
of the air, will rapidly become covered with a scale of oxyd, or rust. A stick 
of charcoal may be kept in oxygen at common temperatures for years with- 
out entering into combination with the gas, but the smallest spark upon 
the surface of the coal will cause the two elements to unite with great 
rapidity. 

The direct union of oxygen with a substance is always 
attended with an evolution of heat. 

In the ordinary rusting of iron, the disengagement of heat is too slow and 
feeble to be readily perceptible ; but in some instances, where the union with 
oxygen at ordinary temperatures is rapid, the heat accumulates, and often- 
times rises sufficiently high to cause the materials to burst into a flame, pr^ 
ducing what are called cases of " spontaneous combustion." This phenomenon 
is often exhibited when tow, " cotton- waste," or other fibrous materials that 
have been used in lubricating machinery, are laid aside in heaps. The oil 
upon them being spread over a large surface, absorbs oxygen with great rap- 
idity, and the temperature of the mass continues to increase until the whole 
bursts into flame. Charcoal, reduced to a fine powder and exposed to the 
air, moist hay in stacks, and damp cloths in bales, frequently take fire under 
the same circumstances. 

When the direct union of oxygen with a substance is 
attended with an evolution of both light and heat, the 
process is called Combustion, and the body is said to 
burn. On the other hand, the body which can combine 
with oxygen under such circumstances, is termed a Com- 
bustible, and the oxygen a supporter of combustion. 

All the ordinary forms of combustion are simply processes of oxydation, 
and are accompanied by a withdrawal of free oxygen from the surrounding 
air ; and in most instances the oxydation is commenced, or, as we express it, 
" the fire is kindled," by the application of some ignited substance, which 
raises the temperature of the combustible body sufficiently to enable it to at- 

Qtjestioxs. — In order to commence and carry on oxydation, -what is generally neces- 
sary ? What are examples? What phenomenon always accompanies the direct union of 
oxygen with a substance ? What is spontaneous combustion ? Give examples. What 
do you understand by the ordinary meaning of the term combustion*? What is a combus- 
tible body ? Why is it generally necessary to apply heat in order to cause combustion to 
commence ? 



190 



INORGANIC CHEMISTRY. 




tract the oxygen of the air, or commence burning ; afterward, the heat which 
is liberated during the process is more than sufficient to carry it on r and thus 
the combination of one portion of oxygen with a burning body, causes tho 
absorption of another portion.* 

Bodies which will burn in the air, together with many substances which 
are generally considered as incombustible, burn in oxygen gas with great 
splendor. Experiments illustrative of these facts are among the most bril- 
liant and interesting in the whole science of chemistry. 

If we blow out a lighted candle in tho air, the wick continues 
to glow for a few moments, but the flame does not sponta- 
neously re-appear. If, on the contrary, the candle, still pre- 
senting some incandescent points, be plunged into a receiver 
containing oxygen (see Fig. 81), it inflames instantly, and 
bums with great brilliancy. This experiment, which may bo 
repeated with a small narrow mouth jar of oxygen a great num- 
ber of times, is characteristic of pure oxygen, and is the princi- 
pal test used to detect its presence. 

A glowing slip of wood introduced into oxygen, bursts into 
i'rne with a slight detonation. A bit of charcoal bark, slightly ignited, at- 
tached to a wire and lowered into a jar of oxygen, burns with great rapidity, 
sending off showers of brilliant scintillations in all directions. If a moistened 
slip of litmus paper (§ 266) be introduced into the jar after the combustion, 
it immediately turns red, a change not affected by atmospheric air, or pure 
oxygen ; consequently an acid gas has been formed from the charcoal and tho 
oxygen, which is called carbonic acid. 

The combustion of iron in oxygen constitutes a 
most beautiful experiment. For this purpose a 
piece of fine iron wire, or, what is still better, a 
steel watch-spring, coiled in the form of a spiral 
(see Fig. 82) is employed. One end of the wire 
is tipped with a bit of sulphur, or tinder, and the 
other attached to a cork, so that the spiral may 
hang vertically. The sulphured end is then lighted, 
and the wire suspended in a jar of oxygen, open 
at the bottom, as is represented in the figure, sup- 
ported upon an earthenware plate. The wire burns 
with an intense white light, the oxyd of iron formed ^=| 
darting out in brilliant coruscations in every direc- - 
tion. Melted globules of oxyd occasionally fall off, 
of so elevated a temperature, that they remain red hot for some time under 



Fig 82. 




* For a particular consideration of combustion, see Chapter VII. 



Questions. — How does pure oxygen act on combustible substances? Explain the exper- 
iments detailed. 



OXYGEN 



191 




the surface of water, and fuse deeply into the substance of the plate or 
upon which they strike. 

The light produced by phosphorus burned in 
oxygen is too brilliant and intense to be en- 
dured by the eye ; and the jar, during combus- 
tion, becomes filled with a dense white vapor, — 
phosphoric acid, which is slowly absorbed by 
water. (See Fig. 83.)* 

r Kindled sulphur burns in oxygen with a 
beautiful blue light. 
283. Oxygen and Respiration,— 
Oxygen is necessary to respiration, 
and is constantly taken into the % 
lungs, from the atmosphere, in the 
process of breathing. No animal can live in an atmos- 
phere which does not contain a certain portion of uncom- 
bined oxygen. 

Oxygen, by the chemical action involved in the process of respiration, passes 
from a free state into a state of combination with other substances, and thereby 
becomes unfitted for the further support of animal life. If a bird be con- 
lined in a limited portion of atmospheric air, it will at first feel no inconve- 
nience ; but as a portion of oxygen is withdrawn from a free state at each 
inspiration, its quantity diminishes rapidly, so that respiration soon becomes 
laborious, and in a short time ceases altogether. Should another bird be then 
introduced into the same air, it will be almost immediately suffocated ; or if 
a lighted candle be immersed in it, its flame will be extinguished. Respira- 
tion and combustion both produce the same effect, in causing free oxygen to 
be removed, or absorbed from the atmosphere. An animal can not live in 



t 

; 



* This experiment should he performed with great care ; otherwise the combustion-jar 
is liable to be broken, and the burning, liquid phosphorus dispersed in every direction. 
The combustion ladle should be deep— an iron cup or a piece of chalk scooped out and at- 
tached to a wire, the whole perfectly dry. The phosphorus should be divided under 
water, and afterward dried, not by wiping, but by contact with bibulous paper. It should 
not be allowed to project above the level of the deflagrating ladle, because during the act 
of combustion burning particles might disperse and stick againut the sides of the jar, thus 
infallibly causing rupture of the glass. A similar result might be occasioned by employ- 
ing wet phosphorus, the aqueous moisture from which, by expanding into steam, would 
scatter the melted phosphorus in all directions. One other point should be particularly 
attended to. The phosphorus placed in the ladle, and lowerbd into the jar, should be ig- 
nited on the surface by touching it with a hot wire, and not by holding the whole ladle 
over a flame. These directions being attended to will insure the success of the experi- 
ment, whereas by neglecting them, simple though they may appear, or any one of them, 
failure of the experiment is certain, and danger imminent. — Fauaday. j 



Questions. — Is oxygen necessary to respiration ? What effect has the process of respi- 
ration on oxygen ? Illustrate this. What analogy is there between respiration and com- 
bustion ? 



/ 



192 INORGANIC CHEMISTRY. 

air unfitted to support combustion ; and, under all ordinary circumstances, 
combustion will not continue in air containing too little 0x3 gen for .respira- 
tion. 

Fermentation also acts like respiration and combustion in absorbing free 
oxygen from the atmosphere. 

Although oxygen, as a constituent of the atmosphere, is necessary to respi- 
ration, it is destructive of animal life when breathed for any considerable 
length of time in a state of purity. When a rabbit, for example, is immersed 
in an atmosphere of pure oxygen, it at first experiences no inconvenience, 
but after an interval of an hour, or more, an unnatural excitement of the sys- 
tem is occasioned, accompanied by a rapid respiration and circulation of the 
blood ; this is soon followed by insensibility, and death ensues in from six to 
ten hours. 

284. Magnetism of Oxyge n. — Oxygen is highly magnetic ; that 
is, it sustains the same relations in degree to a magnet, that iron does. It has 
been further proved that, like iron, it loses its magnetism when strongly 
heated, but recovers it when the temperature falls. Faraday computes the 
magnetic effect of oxygen in the air to be equal to that of a metallic shell of 
iron, l-250th of an inch in thickness surrounding the globe of the earth. 

2 85'. Oxygen in Combination . — The force which holds oxygen 
in combination varies extremely in different substances. In silica, (quartz, 
rock crystal, etc.), nearly one half the entire weight of which is oxygen, it is 
combined, or imprisoned, so to speak, with such force, that its liberation can 
only be effected by the most powerful agencies — heat alone failing to produce 
the slightest effect. In other solid oxygenized bodies, however, the affinities 
are so nicely balanced, that the slightest decomposing cause is sufficient to 
rend the elements, as we may say, from each other, and set the oxj^gen free. 
A very striking instance of this is furnished by chlorate of potash, the sub- 
stance generally employed in the production of oxygen — every 124 parts of 
which, by weight, contain, as before stated, 48 of oxygen. A very slight 
degree of heat suffices to overcome the admirably poised balance of affinities, 
by which the combined elements of this salt are held together, and liberate 
every particle of oxygen. But this result can be effected by other agencies. 
For example, if we take a small quantity of sulphur, charcoal, phosphorus, 
sulphuret of antimony, or, to generalize, any other solid which has a strong 
attraction for oxygen, and mix either of them with a little chlorate of pot- 
ash, carefully and with an avoidance of friction, the compound so obtained, 
when struck with a hammer upon an anvil, will explode violently. The ex- 
periment is best conducted by folding the mixture in a piece of paper. With 
phosphorus the explosive violence is greatest, with charcoal least, the varia- 
tion being indicative of the respective tendency of these substances to com- 
bine with oxygen under the circumstances of the experiment. 



Questions. — What effect does oxygen have on animal life -when breathed pure ? What 
is said respecting the magnetism of oxygen ? Illustrate the various conditions under 
which oxygen exists in combination ? 



OXYGEN. 193 

Gunpowder is another example of a substance holding a large amount of 
oxygen in combination, ready to spring into action with an almost irresistible 
violence. 

286. Active and Passive Condition of Oxygen . — Oxygen, 
as hitherto considered, assumes two conditions, or states, widely different from 
each other. These may be termed its active and passive conditions. As 
locked up in rock-crystal, flint, clay, and other solids ; as constituting eight 
ninths of the bland liquid, water ; as an uncombined gas in the atmosphere, 
it is quiescent, inactive, waiting — retaining, however, all its forces in a latent 
state. This inactivity is one extremity of the scale of qualities possessed by 
oxygen. Intense violence characterizes its other extreme condition — " mani- 
fested," says Professor Faraday, " with tremendous energy in the phenomena 
of combustion and explosion — rushing with violence into other forms — dis- 
playing the most glorious exhibitions of light and heat — generating combina- 
tions of characters diametrically opposed, from the extreme of alkalinity on 
the one hand, to the most violent acidity on the other, and finally, having 
gone through its metamorphic phases, assuming its appointed place of rest in 
the world's economy." y. 

287. Ozone . — In addition to these two extreme conditions, oxygen may 
assume another, in some respects still more extraordinary ; — a state in which 
it is neither fully active or fully passive, but intermediate between the two 
former conditions — a state in which the activity possessed is not only less in 
amount, but different in quality. This condition of oxygen is characterized 
by the name of Ozone. 

It has long been noticed that the working of an electric machine, espe- 
cially in a close apartment, was accompanied by a peculiar sulphur-like odor, 
and also, that a similar odor pertained for some little time to places that had 
been struck by lightning. Beside recognizing these facts, and designating the 
odor in question as " the electric smell," no explanation of the phenomenon 
was attempted by scientific men until within a very recent period; (since 1840). 
It was at last noticed, almost accidentally, that if a piece of paper moistened 
with a solution of starch, and a peculiar compound of iodine (iodide of potas- 
sium), was exposed in places pervaded by this odor, it was speedily turned 
blue. Now, this turning blue is an indication of the liberation of iodine from 
its combination ; and the liberation of iodine is an indication of the agency 
of oxygen; so that in the determination of this additional fact, a connection 
was established between oxygen in an active state and — the electric smell. 

The germ of knowledge thus obtained was expanded and generalized by 
Professor Schonbein of Bale, who showed, by carefully conducted experi- 
ments, that the same smell and its corresponding action might be generated 
at pleasure, by various means — that the agent producing the odor occasioned 
other effects beside that of affecting the starch paper, such as bleaching, de- 



Qxtestio^s — Under what two conditions does oxygen generally manifest itself? What 
is the third condition of oxygen ? "What is this condition termed ? What circumstances 
led to the discovery of ozone ? What discoveries were made by Schonbein ? 

9 



194 



INORGANIC CHEMISTRY. 



odorizing, and corroding — and finally, that the mysterious gaseous agency 
itself was neither more nor less than oxygen — oxygen gas existing in a 
marked condition, or, as it is termed, in its allotropic form. — Faraday. 

Preparation . — Ozone may be obtained by passing a succession of 
electric sparks through a tube or vessel containing atmospheric air, or pure 
oxygen gas. It is also produced by the slow action of phosphorus upon oxy- 
gen, or atmospheric air. This latter reaction may be readily demonstrated 
as follows : 

Take a quart glass bottle, and place in it a little water and a stick of 
phosphorus, first demonstrating the absence of ozone by testing it with 
iodine-starch paper.* Close the bottle, and allow the whole to remain for 
a little time. On again immersing the paper slip, it changes color, assum- 
ing a tint of blue. This result is not due to the vapors of phosphoric 
acid which may be noticed in the bottle, as they are readily absorbed by 
passing the gaseous contents of the bottle through water, while the ozone re- 
mains unaltered. 

The formation of ozone may be also shown by another process still more 



Fig. 84. 



simple. Take a glass jar, and first demonstrate 
by the iodine-starch paper the absence of ozone. 
Then pour into the jar a little ether, and there 
is still no ozone ; but if we heat a glass rod in 
the flame of a spirit-lamp, and immerse it moder- 
ately hot (see Fig. 84), ozone will be abundantly 
produced. 

Prop e l r ties . — Ozone has never been ob- 
tained in a separate state, and appears to be 
entirely insoluble in all liquids. It has a pecu- 
liar odor, whilst ordinary oxygen is totally devoid- 
of all smell. It possesses powerful bleacning 
.ggr properties, and if a solution of sulphate of indigo 
|f be poured into a vessel containing ozone, its 
deep blue color is destroyed with great rapidity. 
If the same experiment be tried with common 
oxygen, no bleaching action takes place. Ozone also exercises a remarkable 
influence over certain odors ; thus, if a piece of tainted meat be immersed in 
^bds-gas. (see Fig. 85) the effluvium is instantly destroyed. 
\Ozone is perhaps the most powerful of all oxydizing agents. It corrodes 
even orga nic - U> dies, such as cork and India-rubber, while fragments of iron, 
copper, etc., rapidly absorb it, and become converted into oxyds. Silver, 




* Iodine starch paper may be simply prepared by mixing a little starch -with a solution 
of iodide of potassium — a salt obtained of any druggist — and imbuing unsized paper with 
the compound. 



Questions. — How may ozone be obtained ? What are the properties of ozone 
is said of the qxydizing influences of ozone ? 



What 



OXYGEN. 



195 



Fig. 85. 



under ordinary circumstances, is not 
affected by oxygen, and has hence 
been considered as one of the noble 
metals; but if a piece of silver-foil, 
moistened with water, be plunged 
into ozone, it rapidly crumbles into 
dust — oxyd of silver. Ozone dis- 
places iodine from its combinations 
with the metals, setting the iodine 
free. This reaction is so easily pro- 
duced, and is so sensitive, that it fur- 
nishes the readiest and most delicate 
method of detecting the presence of 
traces of ozone in the air. A slip of 
paper, as before stated, moistened with 
starch and iodide of potassium, and 
inserted in a vessel containing the 
slightest admixture of ozone, becomes 

blue from the action of the liberated iodine, which immediately unites with 
the starch, and forms the blue iodide of starch. 

One of the most singular circumstances connected with ozone is the effect 
of heat upon it. A temperature not much higher than boiling water is suf- 
ficient to destroy it entirely. Advantage is taken of this fact to demonstrate 
the absolute chemical identity of ozone and oxygen. Ozone passed into one 
end of a red hot tube comes out ordinary oxygen at the other end.* 




" Respecting this strange condition of allotropism, of which ozone is a particular ex- 
ample, Professor Faraday, in a recent publication, remarks : — " There was a time, and 
that not long ago, when it was held among the fundamental doctrines of chemistry, that 
the same body always manifested the same chemical qualities, excepting only such va- 
riations as might be due to the three conditions of solid, liquid, and gas. This was held 
to be a canon of chemical philosophy as distinguished from alchemy ; and a belief in the 
possibility of transmutation was held to be impossible, because at variance with this fun- 
damental tenet. But we are now conversant with many examples of the contrary ; and, 
strange to say, no less than four of the non-metallic elements, namely, oxygen, sulphur, 
phosphorus, and carbon, are subject to this modification. The train of speculation which 
this contemplation awakens within us is extraordinary. If the condition of allotropism 
were alone confined to compound bodies, that is to say, bodies made up of two or more 
elements, we might easily frame a plausible hypothesis to account for it ; we might as- 
sume that some variations had taken place in the arrangement of their particles. But 
when a simple body, such as oxygen, is concerned, this kind of hypothesis is no longer 
open to us; we have only one kind of particle to deal with, and the theory of altered 
position is no longer applicable. In short, it does not seem possible to imagine a rational 
hypothesis to explain the condition of allotropism as regards simple bodies. "We can only 
accept it as a fact, not to be doubted, and add the discovery to that long list of truths 
which start up in the field of every science, in opposition to our most cherished theories 
and long-received convictions." 



Questions. — What reaction takes place when ozone turns iodine-starch paper blue ? 
What effect has heat upou ozone ? How is ozone proved to be simply modified oxygen ? 



196 INORGANIC CHEMISTRY. 

Ozone may be generally recognized in air which has swept over the ocean, 
although generally absent in air which has swept over land. It would ap- 
pear that a moist state of the atmosphere is necessary to its development.* 
Mr. Wise, the celebrated aeronaut states, that when on one occasion during 
an ascension, he became enveloped in a thunder-cloud, he found the surround- 
ing air most powerfully impregnated with the peculiar odor of ozone. 

It can not be doubted that so active an agent as ozone present in the at- 
mosphere, must exercise an important influence in the economy of nature. 
What this influence is, is not definitely known. There can be but little 
doubt, however, that it acts as a purifying agent — oxydizing or burning up 
noxious products floating in the atmosphere. This supposition coincides with 
the opinion extensively entertained, that when ozone is in excess in the air, 
diseases of the lungs, influenza, etc., prevail (as would be expected from its 
irritating character) : and that when it is deficient, fevers, etc., are common. 
Observers generally agree, that during those seasons in which cholera rages, 
the quantity of ozone in the atmosphere is greatly diminished. 

2S8. Daily Consumption of Oxygen . — " It is not easy," says 
Professor Faraday, "to form an adequate idea of the aggregate results ac- 
complished by oxygen in the economy of the world. For the respiration of 
human beings alone, it has been calculated that no less than one thousand 
millions of pounds of oxygen are daily required, and for the respiration of ani- 
mals double that quantity ; whilst the processes of combustion, fermentation, 
decay, and the like, continually going on, increase the daily sum total to eight 
thousand millions of pounds. Reduced to tons, we have the figures 1, 142, 847 
as representing the daily consumption, and 2,609,285,714 the yearly consump- 
tion. Taken in connection with these statements, the fact that from one half 
to two thirds of the bulk of all the matter upon our planet consists of oxygen, 
does not seem wonderful. 

SECTION II. 

MANAGEMENT OF GASES. 

289. Pneumatic Trough , — For collecting gases not absorbed to 
any considerable extent by water, an arrangement, known as the Pneumatic 
Trough, is always employed. For small operations this apparatus may be simply 
constructed by fixing a perforated shelf within a shallow dish, or wooden tub, 
in such a way, that when the vessel is filled with water to the proper height, 



* Prof. Smallwood, of Montreal, in a communication to the American Association for 
the Advancement of Science, in 1S5T, stated that during the seven years ending in 1S56, 
there were at Montreal, 918 days on which rain and snow fell ; and during the like period, 
there were 816 days on which ozone was present in the air in appreciable quantity. 

Questions. — Under what circumstances is ozone noticed in the atmosphere ? What 
influence is ozone supposed to have in the economy of nature? What is said respecting 
the daily consumption of oxygen ? How are gases not absorbed by water collected ? De- 
scribe the pneumatic trough. 



MANAGEMENT OF GASES. 



191 



Fig. 86. 








the shelf will be covered by it to the depth of about 
an inch. (See Fig. 86.) Another and more elegant 
arrangement, constructed of glass, and suitable for j 
a lecture table, is represented by Fig. 87. The 
vessel intended for the reception of gas is filled with 
water, inverted and placed upon the shelf of the 
pneumatic trough, with its mouth directly over the 
perforation in it. The extremity of the gas-delivering 

-p IG , gY tube, which dips into the water, 

is brought directly beneath the 
shelf, in such a way that the 
bubbles of gas escaping, ascend 
through the opening in the shelf 
into the vessel above. 

For permanent use, the pneu- 
matic trough is usually construct- 
ed on a larger scale, of copper or 
tin plate, or of wood, and fur- 
nished with perforated shelves, 
arranged below the water level, 
of sufficient extent to accommo- 
date a number of gas receivers at the same time. Fig. 88 represents the con- 
struction of such a pneumatic trough. 

Water is supported in 
the gas-receivers above 
the level of the pneu- 
matic trough by reason 
of the pressure of the 
atmosphere, on the 
same principle as mer- 
cury is sustained in the 
tube of a barometer. 

In the collection of 
gases over the pneu- 
matic trough, it should 
be observed that the 

gas which first comes over is mixed with the atmospheric air of the generating 
vessel, or retort ; hence a volume of gas equal to about twice the volume of 
the retort should be allowed to escape, as impure^ This .precaution is espe- 
cially to be attended to in the case of gases (such as hydrogen) which form 
explosive mixtures with atmospheric air. Gases may be transferred from one 
vessel to another, over the pneumatic trough, with the utmost facility, by 
first filling the vessel into which the gas is to be passed "with water, inverting 
it, carefully retaining its mouth below the water-level, and then bringing 

Questions. — What, precaution should be observed in collecting gases over a pneumatic 
trough ? How may gases he transferred from one vessel to another ? 



FIG. 88. 




198 



INORGANIC CHEMISTRY. 



Fig. 89. 




beneath it the mouth of the ves- 
sel containing the gas. (See Fig. 
89.) On gently inclining the 
latter, the gas passes into the 
second vessel. 

Ajar, wholly or partially filled 
with gas at the pneumatic trough, 
may be removed by placing be- 
neath it a common plate, deep 
enough to contain sufficient 
water to cover the edges of the jar. 
In this way gas, especially oxy- 
gen, may be preserved for a con- 
siderable length of time without 
admixture with the external air. 
290. Gasometers . — In order to collect and preserve large quantities 
of gas, and to experiment with them more conveniently, capacious vessels of 
sheet-iron, or copper, called gasometers, are used. They consist in general 
of a cylindrical reservoir, suspended 
with its mouth downward, and fit- 
ting into an exterior and larger cyl- 
indrical vessel, or cistern, filled with 
water, as is shown in Fig. 90, which 
represents a pair of gasometers. The 
inner cylinder moves freely in the 
outer one, rising and falling as the 
gas is forced in or pressed out. The 
posts on each side of the cylinder 
are hollow, and contain weights, 
suspended to and balancing the in- 
ner moveable cylinder, so that it 
only presses on the gas as required. 
An upright rod of metal, shown in 
the engraving, rising from the inner 
cylinder, and passing through the 
supporting frame-work, keeps the 
cylinder steady in its place, as it 
rises or falls. Pressure, for forcing 
out the gas, is obtained by slipping 
on to this rod slit- weights of iron, as 
is seen in the figure. Gas is introduced into, and discharged from the gas- 
ometer, by means of a metal pipe, furnished with stop- cocks, and entering at 
the bottom of the stationary cylinder. For convenience, this pipe is carried 
up in front of the gasometer on the outside (as seen in the engraving), and by 




Questions What are gasometers ? How are they constructed ? 



HYDROGEN. 



199 



means of flexible tubes of India-rubber or gutta-percha, which screw on to its 
extremity, the gas can be conducted to any distance and in any direction. 

The stop -cocks seen at the bottom of the gasometer are for the purpose of 
letting off the water, whenever this becomes necessary. 

The large gasometers used for the collection and storage of illuminating gas 
are constructed upon precisely similar principles. Their general construction 
is represented in Fig. 91. The gas from the retorts is conducted by a pipe 

Fig. 91. 




into the interior of the gasometer, and elevates it. Another pipe, opening 
also into the interior, is connected with the service-pipes which supply tho 
gas. The gasometer is balanced by counter weights, supported by chains, 
which pass over pulleys, and just such a preponderance is allowed to it as is 
sufficient to give the enclosed gas the compression necessary to drive it through 
the pipes to the remotest part of the district to be illuminated. 



SECTION III. 



HYDROGEN. 






Equivalent 1. Symbol H. Density 0-0692 (Jir=l.) 

291. History, — rHydrogen was first correctly described 
by Cavendish, an English chemist, in 1766. Before this] 
it had been confounded with several of its compounds, 
under the designation of inflammable air. Its name is 
derived from vdcog, water, and yevvao), I give rise to, and 
refers to its production of water by uniting with oxygen. 

Questions. — What is the history of hydrogen ? What is its equivalent, symbol, and 
density ? 



200 



INORGANIC CHEMISTRY 



292. Natural History and Distribution.— Hydrogen is 
^nev.er found in nature in a free state. The substance 

which contains it in the greatest abundance is water, of 
which it forms one ninth part by weight. As a constituent 
v of other inorganic bodies, it is not very abundant in nature, 
but in the organic kingdom it enters largely into the com- 
position of most animal and vegetable substances. 

293. Preparation. — Hydrogen is always obtained for 
practical or experimental purposes from the decomposition 
of water. 

It is liberated in the state of greatest purity through the agency of the vol- 
Fig. 92. taic current. When the wires connecting the poles 

of a galvanic battery in action are caused to terminate 
in water, decomposition is occasioned — hydrogen 
being evolved at the negative pole and oxygen at the 
positive. (See § 242, p. 148.) By placing tubes 
filled with water over the respective poles (see Fig. 
92) the two gases may be coUected in a separate 
state. 

"Water can not, under all ordinary circumstances, 
be decomposed by the action of heat alone.* Hydro- 
gen may, however, be separated from water by heat- 
ing this fluid in contact with substances which absorb its oxygen. Thus, if 
the vapor of water (steam) is passed over finely divided iron, heated to bright 
redness, the water is decomposed, oxygen uniting with the iron to form oxyd 
of iron, and hydrogen being set free. 

This experiment, which was devised by Lavoisier, in order to prove that 




water is a compound substance, is 
easily performed by placing a quantity 
of iron filings in an iron tube (a gun- 
barrel, or better, a porcelain tube, 
protected by a covering of sheet-iron), 
arranged in a furnace, as is represent- i 
ed in Fig. 93 ; one end of the tube 
connected with a retort, or flask, 
containing a small quantity of water, 
from which, by the heat obtained from 



Fig 




* Mr. Grove, the eminent English physicist, has recently shown that the vapor of water 
is decomposed to a small but sensible extent by an exceedingly high temperature, and 
resolved into its constituent gases. 

Questions. — What is said of its natural history and distribution ? How is hydrogen 
obtained? What process yields it in the greatest purity? Under what circumstances 
can water be decomposed by heat? Describe the experiment of Lavoisier. 



HYDROGEN. 



201 



Fig, 




a spirit lamp, a current of steam is driven through the tube, at the moment 
the metal has attained a full red-heat. 

If the conditions of this experiment are reversed, and a stream of hydrogen 
be made to pass over oxyd of iron heated to redness, the hydrogen unites 
•with and removes the oxygen of the oxyd of iron, thereby leaving metallic 
iron, and producing water. 

If we sprinkle water in small quantity upon red-hot coals, a portion of it 
will be decomposed on the same principle as in the above experiment. The 
oxygen combines with the carbon and increases the intensity of the fire, 
while the liberated hydrogen burns and develops a very high degree of heat. 
Blacksmiths, it is well known, are accustomed to sprinkle their fires with 
water, in order to augment the heat, and too little water thrown upon a confla- 
gration will often produce more injury than benefit. 

Some of the metals, such as potassium and sodium, are capable of decom- 
posing water (combining with the oxygen and liberating hydrogen), without 
the aid of heat. This may be shown by the following ex- 
periment : 

Fill a glass tube with water, from which the air has been 
expelled by boiling, and invert it in a vessel of water. Pass 
into the mouth of this tube, by means of a wire, a small 
piece of sodium, as is represented in Fig. 93. This metal, 
being lighter than water, ascends to the surface, and absorb- 
ing oxygen from the water, rapidly liberates hydrogen. 

Hydrogen gas is most conveniently obtained by putting pieces of zinc \ 
or iron into oil of vitriol, or strong sulphuric acid, diluted with six or eight 
times its bulk of water. Practically, this process may be conducted as fol- 
lows : — Introduce into a suitable jar or bottle a small quantity of sheet zinc 

(or in the absence of zinc, scraps of iron, 
nails, etc.) cut into small pieces, together 
with water sufficient to more than cover 
the same. Then add a small quantity of 
strong sulphuric acid, and the evolution of 
gas immediately commences. By inserting 
into the opening of the flask, a perforated 
cork, to which a bent glass tube is fitted 
(see Fig. 95), the gas is easily collected 
over water in the usual way. Particular 
care should, however, be taken not to ad- 
mit the gas into a receiver, until all the at- 
mospheric air in the flask has been expelled. 
An ounce of zinc is sufficient to liberate 
from water about two and a half gallons of / 

Questions. — Why does a blacksmith sprinkle his fires with water ? Do any of the 
metals decompose water without the aid of heat ? "What experiment illustrates this fact ? 
How is hydrogen obtained most conveniently ? Describe the practical performance of this 
process ? 

9* 








202 INORGANIC CHEMISTRY. 

hydrogen, and the evolution of the gas is regulated by the supply of acid. By 
means of a funnel-tube fitted into the cork of the generating vessel, and de- 
scending within the vessel to a point below the level of the contained' liquid 
(see Fig. 96), the acid may be added from time to time in exactly the 
quantities necessary to produce the best effect. No gas can escape by this 
p funnel-tube, as its extremity within the vessel is always cov- 

ered by the fluid. 

The theory of the liberation of hydrogen in this process is as 
follows : neither zinc nor iron is capable of uniting directly, as 
a metal with sulphuric acid ; but oxyd of zinc and of iron 
combine readily with it. Thus a decomposition of water is 
determined. The zinc or iron takes oxygen from the water, 
and forms oxyds of these metals respectively, whDe the hydro- 
gen before in combination with the oxygen passes off in tho 
gaseous form. The oxyds of zinc and iron formed are inso- 
luble in water, but are readily dissolved by the sulphuric acid, 
forming salts of sulphate of iron or zinc. The surface of the metal is thus left 
clean and exposed to the water, from which it attracts another portion of 
oxygen, which is dissolved as before. The reaction which takes place may 
be expressed by the following equation : — 

Zn-f S0 3 +HO=Zn 0, SOs-j-H. 
Sulphuric acid does not take any direct part in the decomposition of tho 
water; but its presence seems to facilitate the processes by increasing the af- 
finity between the metal and the oxygen of the water ; it also dissolves tho 
oxyd as fast as it is formed, which is essential to the continuance of the ac- 
tion. 

294. Properties . — Hydrogen is a colorless gas, which has never been 

liquefied. "When pure, it is without taste or odor, but as prepared in the way 

last described, itTiasaT nauseous, disagreeable odor, arising from the presence 
of impurities contained in the materials used. It is slightly soluble in wat 



and does not support respiration : an animal plunged in it soc 
of oxygen. When mingled with a large quantity of air, it may be breathed 
for a time without inconvenience, and tho voice of the person inhaling it, ac- 
quires a peculiar shrill squeak. Sounds produced in this gas are hardly per- 
ceptible. 

Hydrogen is the lightest substance in nature, being sixteen times lighter 
than oxygen, and 14-4 lighter than air ; 100 cubic inches of it weigh only 
2*14 grains. Owing to its levity, it has been extensively used in filling bal- 
Uojffig, which begin to rise when the weight of the material of which they 
Tare made and the hydrogen together, are less than the weight of an equal 
bulk of air. At the present time, coal gas, owing to the greater facility with 
which it can be obtained, is generally substituted in the place of hydrogen for 



/ 






Questions. — "What is the theory of the liberation of hydrogen under such circumstances ? 
What is the chemical reaction ? "What part does the sulphuric acid sustain ? What are 
the properties of hydrogen ? What is said of the lightness of hydrogen ? 



HYDROGEN 



aerostatic purposes — although of much greater density. Soap-bubbles inflated 
with hydrogen rise rapidly through the air. In order to obtain these bubbles, 
wo fill a bladder, or gas-bag, provided with a stop-cock, with hydrogen gas, 
and attach to the stop-cock a common tobacco-pipe, or what is better, one of 
metal. (See Fig. 99.)* The extremity of the pipe is dipped into soap-suds, 

,nd the bubbles are blown by opening the stop-cock and gently pressing tho 
bladder. 

Hydrogen, beside being th ft lightest; bo dy in nature, possesses also tho 
ity, and there is reason for supposing that its atoms or molecules 
are smaller than those of any other known substance. No receptacle that is 

t all porous, as a bladder or India-rubber bag, can be used for storing hy- 
drogen for any considerable length of time, the remarkable law of the diffu- 
sion of gases already explained (§ 52, p. 3-9) promoting its escape, and caus- 
ing an interchange of the surrounding air. / Faraday, in an attempt to liquefy 
hydrogen through the agency of cold and pressure, found that it would leak 
freely with a pressure of 23 atmospheres through. .stop-cocks which,jKera„per- 
fectly tight with nitrogen at 60 atmospheres. A minute crack in a glass jar, 
quite too small to leak "with water, will allow hydrogen to escape readily. 
Hydrogen also enters into combination in a smaller proportionate weight than 
any other element, and has hence, been chosen as the unit of the scale of 
equivalents. Owing to the lightness of hydrogen, a jar may be 
filled with it by displacement, without using the pneumatic 
trough. Thus, if a bottle or jar be inverted over the extremity 
of an upright tube delivering the gas (see Fig. 97), the air it 
contains will be entirely displaced by the hydrogen rising into 
it. The gas may be retained for some minutes, even when re- 
moved from the source of supply, provided the jar be still held 
in an inverted position ; but if its mouth be turned upward, the 
gas almost immediately escapes. N v ' 

295. Combustion of Hydrogen . — Hydrogen is ex- 
tremely inflajnnaajolej^ when a lighted taper is plunged into a 
jar of it, the gas takes fire, but the taper is extinguished, since 
there is no oxygen above the mouth of the jar to support com- 
bustion. This experiment is best shown by thrusting up a 
lighted bit of candle into an inverted jar, or bottle of hydrogen. 
The ignited gas burns quietly at the mouth of the jar, and the extinguished 
candle may be again relighted by it. If the bottle is suddenly reversed after 
the gas has burned awhile, the remaining gas will burst into flame with a 
slight explosion. 




* India-rubber gas-bags, with metal pipes, stop-cocks, etc., are prepared especially for 
tbis purpose by dealers in chemical apparatus. A tobacco-pipe attached to the India- 
rubber delivery-tube of a gasometer may also be employed. 



Questions. — What of its tenuity and smallness of particles? What are some illustra- 
tions of these properties ? Why has hydrogen been chosen as the unit of the scale of 
equivalents ? What is said of the inflammability of hydrogen ? 



204 



INORGANIC CHEMISTRY. 



V 

• 




A jet of hydrogen burns with a bluish white flame, and a feeble light. The 
experiment can be shown by adapting to the cork of a flask from which hy- 
FiG. 98. drogen is evolved, a piece of pipe-stem, or a small glass tube 
drawn out to a point. (See Fig. 98.) 

If a dry, cold tumbler be held over a jet of burning hydro- 
gen, its interior will rapidly become covered with a copiou3 
deposition of moisture. This results from a condensation of 
the vapor of water produced by the union of the hydrogen 
with the oxygen of the atmosphere. 

296. Explosion of Mixed Oxygen and Hy- 
drogen . — If the hydrogen before being kindled is mixed 
with air sufficient to burn it completely, or with between two 
and three times its volume, and then ignited, combustion takes 
place instantaneously throughout the whole mass, and is attended with a vio- 
lent explosion. Hence particular caution is necessary in using hydrogen to 
avoid the slightest admixture of common air. 

"When pure oxygen is substituted in the place of air, the explosion is much 
more violent. 

A mixture of oxygen and hydrogen will never unite under ordinary cir- 
cumstances of temperature and pressure ; but the passage of an electric spark, 
or the application of an intensely heated body, will cause instantaneous union, 
accompanied by an explosion. The product of such combination is always 
water. 

In illustrating by experiment the explosive combination of oxygen and hy- 
drogen, the proportions which produce the best effect are 2 of hydrogen to 5 
of air, or 2 of hydrogen to 1 of oxygen. As the explosions are most violent, 
small quantities only of the mingled gases can be safely employed. 

The experiments may be varied by inflating a soap-bubble with the gas- 
eous mixture, and igniting it 

with a candle as it ascends ; ^ lG ' °^* 

or by blowing up a quantity 
of bubbles in a shallow clish, 
as is represented in Fig. 99; 
or by filling a bladder with 
the mixed gases, and ignit- 
ing it from a distance by 
means of a candle fixed to --s§ril 
the end of a pole. 

What is called the hydrogen-gun consists of a strong tin tube, about an 
inch in diameter and eight inches in length, open at one end and provided 
with a small vent hole at the other. In loading it, the vent is stopped by 




Questions. — "What are the peculiarities of the hydrogen flame? If a cold glass tum- 
bler be held over the jet, -what phenomenon is noticed ? If hydrogen, before ignition, be 
mingled with air, what happens? "Will oxygen and hydrogen unite of their own accord? 
What are the best explosive mixtures of oxygen and hydrogen ? How may the explosive 
effects of mixed hydrogen and oxygen be illustrated ? Explain the hydrogen-gun. 



HYDROGEN. 205 

wax, the tube filled with water, and the proper mixture of gases introduced 
from a receiver under water. The tube thus rilled is closed with a cork, and 
afterward fired at the vent. The explosion is sufficient to expel the cork 
with violence, and produce a loud report. The same experiment may be 
more simply performed by inverting a vial, or test tube over a jet of hydro- 
gen, and allowing the escaping gas to mingle with, but not wholly displace the 
air. The mixture thus obtained may be exploded by applying flame to the 
mouth of the tube. 

The loud, sharp report which attends the combination of oxygen and hy- 
drogen under these circumstances, is explained as folio ws : — The steam, which 
is the resulting product of the union, suddenly expands from the high tem- 
perature attendant on the combustion, and immediately afterward condenses ; 
great dilatation is first produced, followed by the formation of a partial vacuum ; 
the surrounding air rushes in to fill the void, and by the collision of its par 
tides produces the report.* 

The inflammation of an explosive mixture of oxygen and hydrogen, dr of 
hydrogen alone, in contact with air, is not only effected by a lighted taper, or 
the electric spark, but it likewise takes place in the cold by the action of cer- 
tain substances, the principal of which is "platinum sponge," or platinum in 
a loosely coherent state, f 

If we throw a piece of platinum sponge into a vessel containing a mixture 
of 2 parts of hydrogen to 1 of oxygen, a combination of the two gases, ac- 
companied by an explosion immediately ensues. The same thing also takes 
place, but more slowly, when a thin plate of platinum, rendered chemically 
clean, is employed. 

This phenomenon has been considered as one of catalysis (p. 161), or in 
other words, as due solely to the mere presence of the platinum ; but it is 
now generaUy believed to be the result of adhesion (§ 48). The gasps, it is sup- 
posed, by reason of a strong adhesion to the metal, are condensed upon its 
surface, and being thus brought within the sphere of each other's attraction, 



* " The whole range of natural phenomena," says Professor Faraday, " does not pre- 
sent a more wonderful result than this violent combination of oxygen and hydrogen. 
Well known and familiar though it be — a fact standing on the very threshold of chem- 
istry — it is one which I ponder over again and again with wonder and admiration. To 
think that these two violent elements, holding in their admixed parts a force of the most 
extraordinary kind — a force which, if we reduce it to a certain kind of comparison, will be 
found equal to the power of many thunder-storms — should wait indefinitely until soma 
cause of union be applied, and then furiously rush into combination, and form the bland, 
unirritating liquid, water ; — is to me, I confess, a phenomenon which continually awakens 
new feelings of wonder as often as I view it." 

t Platinum sponge is easily prepared by soaking a small piece of bibulous paper in a 
solution of platinum (the bi-chloride of platinum) and afterward drying and igniting it. 
A little pellet of asbestos may be substituted with advantage in place of the paper. The 
Bponge, after a little time, loses its peculiar property, but it can be again restored by being 
strongly ignited. 

Questions. — What occasions the detonation? How may a mixture of oxygen and hy- 
drogen be exploded without the direct application of an ignited substance ? What ia 
spongy platinum ? What experiment illustrates its action f 



206 



INORGANIC CHEMISTRY. 



Fig. 100. 



unite. By the act of combination heat is evolved — the platinum becomes 

red hot — the remaining uncombined gases are ignited by it, and an explosion 

occurs. 

Other finely divided substances beside platinum possess this property of 

favoring the combination of oxygen and hydrogen in an inferior degree. 

Even pounded glass, charcoal, pumice, rock-crystal, etc., if warmed to 600° 

F. produce this effect. Finely divided palladium, rhodium, and iridium act 

in the same manner as platinum. 

If we project a jet of hydrogen alone upon platinum sponge, this substance 

becomes incandescent, and the gas inflames. 

297. Dobereiner's Inflammable L a m p . — Advantage has 
been taken of this circumstance to construct a machine for 
obtaining fire instantly by means of hydrogen gas. It 
consists of a conical glass, Fig. 100, attached to a plate and 
stop-cock, and suspended in a receiver, a, containing sul- 
phuric acid and water. Within the inner vessel a piece of 
zinc, z, is suspended, and this by contact with the dilute 
acid evolves hydrogen. The gas accumulating in the in- 
ner vessel forces the acid into the outer vessel, until it no 
longer touches the zinc, and thus stops the further evolu- 
tion of hydrogen. By opening the stop-cock, c, the accu- 
mulated gas issues upon a ball of spongy platinum, d, and 
almost immediately takes fire. As fast as the gas escapes 
from the interior vessel, the sulphuric acid which has been 

displaced rises to take its place, and again coming in contact with the zinc, 




Fig. 101. 



evolves a fresh supply of hydrogen. 

298. Musical Tones . — If a glass tube, open at 
both ends, be held over a jet of burning hydrogen (see Fig. 
101), a rapid current of air is produced through the tube, 
which occasions a flickering of the flame, attended by a 
series of small explosions, that succeed each other so rap- 
idly, and at such regular intervals, as to give rise to a 
musical note, or continuous sound, the pitch and quality 
of which varies with the length, thickness, and diameter 
of the tube. By sounding the same note with the voice, a 
tuning-fork, or musical instrument, the singing of the 
flame may be interrupted, or caused to cease entirely ; or 
when silent, to recommence. 

299. Heat Generated by the Combustion 
of Hydrogen . — The flame of hydrogen, although 
slightly luminous, produces a great degree of heat. When 
the combustion is assisted by oxygen gas, the heat gen- 

Questions.— What other substances possess similar properties ? When a jet of hydro- 
gen is thrown upon spongy platinum, what ensues ? What is the construction of Dobe- 
i-einer's lamp ? When hydrogen is burned from a jet in a tube, -what phenomenon is no- 

di. ? What is said of the heating effects of the hydrogen flame ? 




& 



HYDROGEN. 



207 



Fig. 102. 



erated is most intense, and is only exceeded by that produced by electrical, 
agency. 
300. Oxy hydrogen Blow-pipe. 

— The practical arrangement for effecting 

the combustion of hydrogen by oxygen, 

is known as the " Oxy hydrogen" or 

" Compound" Blow-pipe. As commonly 

constructed, it consists of two gasometers, 

containing, the one oxygen, and the other 

hydrogen. (See Fig. 102.) Tubes leading 

from these are brought together at their 

extremities, and the two gases delivered 

from apertures situated l-30th of an inch 

apart, are burned in a single jet. The 

best result is attained by so arranging the 

stop-cocks of the gasometers, that the 

volume of hydrogen flowing out shall be 

double that of the oxygen. 

The effects of the compound blow-pipe 

may be produced in a degree by passing 

a stream of hydrogen through the flame 

of a spirit-lamp, as is represented in Fig. 

103. 

The effects of the oxyhydrogen blow- 
pipe are very remarkable. Substances that are infusible in the most intense 
Fig 103 blast furnaces, melt in the heat of 

its focus with the rapidity of wax. 
Iron, copper, zinc, and other metals, 
melt and burn in it readily; the 
first (when a watch-spring or steel 
file is employed) with beautiful scin- 
tillations, and the latter with char- 
acteristic colored flames. Thick 
platinum wire melts in it with ease, 

and may be even volatilized. Rock-crystal can be liquefied and drawn out 

into threads like glass, and the stem of a tobacco-pipe may be fused into an 

enamel-like bead. 

When the jet of the two gases, after being set on fire, is directed under 

water, it continues to burn beneath the surface of the liquid, in the form of a 

globe, and fuses and burns metallic wires held in it. 

301. Drum mond Light — The flame of the oxyhydrogen blow-pipe 

is very pale in itself, but diffuses a dazzling light as soon as any solid body 

is introduced into it. By causing the flame to fall upon a cylinder of quick- 





Qtjestions. — Describe the oxyhydrogen blow-pipe, 
duced by it ? What is the Drummond light ? 



What are some of the effects pro- 



208 INORGANIC CHEMISTRY. 

lime, an artificial light is produced, which for whiteness and brilliancy may bo 
compared to the sun itself. "With the requisite supply of gases this light may 
be maintained for hours, care being taken to expose to the flame fresh sur- 
faces of the lime, by causing it to revolve by clock-work continually, but 
slowly. This light is generally known as the " Drummond Light," from the 
name of an English engineer, who first used it for signalizing at great dis- 
tances ; it is also often termed the " lime light." 

The distances at which this light may be seen when its rays are concen- 
trated by a parabolic mirror, are very great. In one instance, during the 
prosecution of the trigonometrical survey of Great Britain, it was seen by 
observers stationed upon a mountain peak, at a distance of 108 miles, during 
daylight. 

The combination of hydrogen with other bodies is not attended with tho 
development of light and heat, with the exception of oxygen and chlorine — 
two of the most highly electro-negative of all known substances. 

302. The Chemical Characteristics of Hydrogen ally 
it very closely with the metals — particularly with zinc and copper — and thero 
are some reasons for supposing that it is itself a metal, exceedingly volatile, 
and sustaining in this respect the same relation to mercury, that mercury 
does to platinum. The fact that it is wanting in luster, hardness, and bril- 
liancy — qualities which are popularly considered as essential attributes of the 
metals — is no argument against this supposition, inasmuch as mercury, when 
vaporized through heat, is as transparent and colorless as hydrogen itself 
The vapor of mercury and of other volatile metals is also, like hydrogen, a 
non-conductor of heat and electricity. Yet mercury, in the state of vapor, is 
no less a metal than in its ordinary condition. 

Although hydrogen is the lightest and the most attenuated substance in 
nature, and combines in the smallest proportional quantity of all the elements, 
its active power, considered in relation to its combining weight, is very great. 
Thus, it combines with chlorine in the ratio of 1 part by weight to 36 ; with 
bromine 1 to 80 ; and with iodine as 1 to 125 ; yet in each case it abun- 
dantly satisfies the combining affinities of the other elements, generates by 
its union powerful and not easily decomposed acids, and in every other re- 
spect manifests an equality of force. This circumstance of so much power 
existing in connection with so little ponderable matter, is, regarded by Pro- 
fessor Faraday, as one of the most remarkable characteristics of hydrogen. 

303. Compounds of Hydrogen with Oxygen. — But two 
compounds of hydrogen with oxygen are certainly known to 
exist *— t he protoxyd of hydrogen, or water, whose chem- 

* According to some authorities, there is a third compound — the suboxyd of hydrogen 
— formed by the gradual absorption of hydrogen by water. 

Questions. — To what distance is this light visible ? Are the combinations of hydrogen 
- generally accompanied by evolutions of light and heat? What is said of the nature of 
hydrogen ? What, according to Faraday, is one the most remarkable characteristics of 
hydrogen ? What compounds does hydrogen form -with oxygen ? 



HYDROGEN. 



209 



ical symbol is HO, and the peroxyd or binoxycl, whose 
symbol is H0 2 . Water is the only natural combination ; 
the binoxyd being an artificial preparation. 

304. \V a t e r is the most important, and at the same time the most re- 
markable of all chemical compounds. It is the most abundant substance ex- 
isting in a separate condition upon the face of the earth, and covers to an 
unknown depth three fourths of its surface. "Water enters largely into the 
composition of nearly all organized matter, and of every structure that pos- 
sesses corporeal vitality, it is an essential element* 

305. Composition of Water . — Water, as has been already stated, 
is formed by the union of two volumes of hydrogen and one of oxygen, or 
by weight, of 8 parts of oxygen to 1 of hydrogen. The composition of water 
by measure and by weight, upon which, as a basis, the whole theory of atomic 
constitution and the doctrine of equivalent proportions rests, may be proved 
by a great variety of experiments, both by analysis and by synthesis. 

By analysis, by decomposing water by the galvanic current (§ 242, p. 148), 
and by passing the vapor of water over red hot iron (§ 293). By synthe- 
sis, by uniting the two gases in proper proportions by combustion — by the 
action of spongy platinum — by the electric spark — and by passing a current 
of hydrogen over oxyd of copper, heated to bright redness. 

The most reliable synthetical process is that last indicated. The hydrogen 
passing over the heated metallic oxyd, combines with its oxygen and forms 
water, which passes off as steam — the copper being left in a metallic state, 
the steam collected and condensed gives the weight of the water formed ; the 
loss in weight which the metallic oxyd experiences gives the weight of the 
oxygen which has entered into the composition of the water ; and the dif- 
ference between these two, gives the weight of the hy- Fig. 104. 
' drogen contained in the water. ' 

Eudiometer . — An apparatus by which a mixture 
of oxygen and hydrogen can be exploded by the electric 
spark, and the resulting product collected and examined, 
is termed an Eudiometer. It consists of a graduated 
v glass tube usually placed over mercury, and so arranged 
^ that an electric spark can be passed into its interior. (See 
Fig. 104.) When a mixture of oxygen and hydrogen is ex- 
ploded in such a tube over mercury, a vacuum is formed 

* A man of 154 lbs. -weight is made up of 116 lbs. of water and only 38 lbs. of dry 
matter: yet this proportion of -water is small in comparison with the amount that enters 
iuto the economy of certain of the lower orders of animals. Of that class of sea-animals 
known as. the medusae, for example, it is estimated that at least 99-100ths of their whole 
structure by weight consists of water. They have, therefore, not inaptly been termed 
" living forms of water." 

QtrESTio^B. — What is said of water ? "What is the composition of water by measure and 
weight ? How is the composition of water proved by analysis ? How by synthesis ? 
What is the most reliable synthetical method, and how is the composition of water calcu- 
lated from the results obtained ? What is an eudiometer ? 



210 INORGANIC CHEMISTRY. 

by reason of their union and condensation, and the mercury rises to fill it. 
If the gases are mingled in the exact proportion to form water, the com- 
bination will be complete, and both will disappear entirely. If, however, 
one of the two elements is in excess, a gaseous residuum will remain. Thus, 
suppose we introduce into the eudiometer 100 measures of hydrogen and 
15 of oxygen, we shall find after combustion 25 of oxygen remaining, but 
none of hydrogen. Therefore, 100 of hydrogen have combined with 50 of 
oxygen, or the union has taken place in the proportion of 2 volumes to 1. 
The graduations marked on the eudiometer tube enable us to proportion 
the quantities of the gases to be introduced, and also to estimate by the 
space unoccupied the volume of the residuum remaining after the combination. %^ 

306. History . — The history of water constitutes one of the most inter-^T 
esting portions of the whole record of physical philosophy. The old Greek 
philosopher Thales, in the earliest dawn of scientific speculation, taught that 
water was the " first and fontal" element of all material things — the earliest 
created substance. At a subsequent period, it was considered to be one of 
four primal elements ; earth, air, and lire being the other three. This view 
of the elementary character of water remained unquestioned until nearly the 
close of the 18th century, or about the time of the first French revolution. 
Von Helmont, a contemporary of Galileo, and one of the most eminent scien- 
tific men of his day, maintained the doctrine that water was convertible into 
earth, and the following experimental results were appealed to as affording 
indisputable evidence of the fact, viz., that a tree when transferred from earth 
to water continues to develop itself and derive solid constituents from the 
liquid ; and that when water- was evaporated to dryness in a vessel, an 
earthy residuum always remained. The inference from these experiments was 
not, however, that water was a compound body, but rather that it possessed 
a generative character, and produced all the elements necessary for vegetable 
existence.* 

Sir Isaac Newton, in 1704. in the course of his optical researches, remarked 
that water and the diamond both refracted light in the same way as sub- 
stances of a highly inflammable character. He in consequence predicted the 



* It is not a little singular that the compound character of water should have remained 
so long undetected by the Egyptians, Greeks, and Romans, who carried some branches 
of economical chemistry to a high degree of perfection, or in later times, by the Arabian 
chemists, or the mediaeval alchemists. It would seem as if the phenomena of vegetation, 
and of animal life, if they had been watched with attention, would have shown that ths 
elementary character of water was a most questionable doctrine. " Not a weed ever grew 
but what was possessed of the secret of its composite nature ; not an animalcule ever lived 
but daily decomposed and changed the ' indivisible' into its own structure. No one, how- 
ever, understood'their language, or tried to interpret it, and hieroglyphics which seem to 
us pictures which tell their own story, revealed nothing to those who had already decided 
that they had no meaning." 
. , j 

Questions. — How may the composition of water be determined by the use of the eu- 
diometer ? What opinions were formerly entertained respecting the nature of water ? 
What doctrine respecting water was advanced by Von Helmont ? Upon what did he base 
his conclusions ? What facts were ascertained by Sir Isaac Newton ? 






HYDROGEN. 211 

future combustion of the diamond, and it is inferred that he anticipated, in 
a like manner, the combustibility of one of the elements of water. 

Three quarters of a century after this, Lavoisier devised and carried out 
an experiment which is regarded as the commencement of the modern sys- 
tem of chemistry. He doubted the conclusions of Von Helmont, "and he 
asked nature if water could or could not be turned into stone, and asked in 
such a way that she granted an intelligible and unmistakable answer. Ho 
took an alembic, which may be described as an air-tight still or retort, in which 
the condensed steam or distilled liquor always flows back into the boiler — 
weighed it — put an ascertained quantity of water in it — made it air-tight — 
and set the water boiling ; the steam or distilled liquor rising, became con- 
densed, and continually trickled back through the tubular arms of the alem- 
bic into the original vessel. This arrangement was kept boiling for ono 
hundred and one days and nights. At the end of that period, the whole ap- 
paratus had lost no weight; the alembic, however, had lost 17 grains, but 
the water had gained weight, and was muddy with earthy particles. "When 
this muddied water was evaporated to dryness, there remained 20 grains of 
earth, IT of which had clearly been worn out of the substance of the vessel ; 
but where had the other 3 come from ? Lavoisier at first assigned them to 
the incidental errors of the experiment, but it was afterward shown that they 
were derived from the water itself — from the saline and organic matter 
which it held in solution. Thus the earth, which Yon Helmont traced to 
the transformation of water, was discovered to have come from the earthy 
vessel in which the water had been continuously boiled. Scheele, an eminent 
Swedish chemist, followed up the experiment, by analyzing the earth pro- 
duced, and proved it to be the same as the material of the apparatus. 

" The notable circumstance in this experiment is the use of the balance. 
Until this weighing of the alembic the balance had not been used in chem-: 
istry as an implement of research. Quality and not quantity was only re- 
garded. But when Lavoisier ordered a balance with a view to its employ- 
ment in research, the fate of old theories was sealed. The very thought of 
the balance implied the perception, by him that thought of it, of the central 
idea of all positive chemistry, namely, that every chemical operation ends in 
an equation ; and that if 100 grains, ounces, or pounds of any substance 
whatsoever are burned, distilled, or in any way altered by a chemical process, 
then 100 pounds, ounces, or grains of material must be accounted for after the 
operation, for nothing is ever lost." — Brewster. 

A few years after this experiment of Lavoisier, oxygen was discovered, 
and hydrogen first correctly described by Cavendish. Subsequently the com- 
position of water was discovered almost simultaneously by James "Watt, the 
inventor of the steam-engine, by Cavendish, and by Lavoisier ; the first two 
by burning hydrogen in oxygen, and the last by decomposing the vapor of 
water. 



Questions. — What experiment was instituted by Lavoisier ? "What were the results of 
this experiment ? What was the most noticeable circumstance attending this experiment? 



212 INOKGANIC CHEMISTRY. 

307. Properties. — The physical properties of water are so well 
known, and hare been discussed to such an extent in the preceding depart- 
ments of this work, that no lengthened description is necessary in the present 
connection. 

In its ordinary condition as a liquid, and free from admixture, water is col- 
orless, transparent, inodorous, and tasteless ; it boils at 212° F., freezes at 
32° F., and evaporates at all temperatures. It is 815 times heavier than 
an equal bulk of air. 

308. Coloration of Water , — The peculiar colors which large bodies 
of water assume have not been satisfactorily accounted for. The color of the 
ocean " on soundings" is generally of a greenish hue ; but off soundings it ap- 
pears blue. It is maintained by some authorities that the blue tint of the 
ocean is only apparent, and is owing to a reflection of the most refrangible 
of the rays of solar light (the blue) in greater proportion than those which are 
less so. Sir Humphrey Davy attributed the blue color of the ocean to an 
admixture of iodine, and others have referred the very remarkable bright blue 
color of the Mediterranean to the presence of salts of copper ; but although 
iodine exists in combination in all sea-water, and copper has been found in 
the waters of the Mediterranean, the quantities present do not appear to be 
sufficient to produce any perceptible coloration. The coloring matter of the 
Eed Sea, which at particular seasons of the year is sufficiently intense to 
justify the appellation bestowed upon this body of water, has been proved to 
be owing to the presence of a prodigious quantity of microscopic plants. 

309. Transparency of the Sea , — The transparency of the sea 
varies with the temperature. The maximum of visibility under water, under 
the most favorable circumstances does not exceed 25 fathoms, or 150 feet. 

310. Purity of Water.— In nature, water is never found 
perfectly pure. 

Rain-water collected in the country after a long continuance of wet weather 
is the purest natural w r ater, but even this always contains atmospheric air, 
and the gases floating about in it, to the extent of about 2% cubic inches of 
air in 100 of water. After rain-water, in the order of purity, comes river- 
water ; next the water of lakes and ponds ; next ordinary spring waters ; and 
then the waters of mineral springs. Succeeding these are the waters of great 
arms of the ocean into which large rivers discharge their volumes, as the 
Black Sea, the water of which is only brackish ; then the waters of the main 
ocean ; then those of the Mediterranean and other inland seas ; and last of 
all, the waters of those lakes which have no outlets, as the Dead Sea, Cas- 
pian, Great Salt Lake of Utah, etc. 

311. S p r i n g Waters . — Spring water, although it may be perfectly 

Qttestions. — "What are the physical properties of water? How much heavier than air 
is water ? To what has the coloration of bodies of water been ascribed ? What is said 
of the transparency of the ocean ? Is water found pure in nature ? "What is the purest 
natural water ? What is the relative purity of different waters ? What is said of spring- 
waters ? 



HYDROGEN. 213 

transparent, always contains more or less of mineral matter dissolved in it. 
The nature of these substances will of course vary with the character of the 
soil through which the water percolates. The most usual impurities are car- 
bonate of lime, common salt, sulphate of lime (gypsum), sulphate and carbon- 
ate of magnesia, and compounds of iron. Most spring waters also contain a 
proportion of carbonic acid gas. 

312. Mineral Springs . — "When the waters of springs retain in so- 
lution so large a proportion of mineral matter as to give them a decided taste, 
they are termed mineral waters, and are usually reputed to have some medi- 
cinal quality, varying with the nature of the substance in solution. 

"Waters which contain iron in quantity sufficient to impart to them an inky 
taste are termed cha-lyb'e-ate; the iron exists in the water most frequently 
in the state of carbonate, dissolved in carbonic acid, and rarely in a propor- 
tion exceeding one grain in a pound of water. 

"Waters impregnated with sulphuretted hydrogen gas are termed sulphurous, 
or sulphuretted; they may be readily recognized by their nauseous taste and 
odor. Remarkable springs of this character exist at Sharon, New York, and 
also in Virginia. 

313. Saline Springs . — Springs whose waters contain a large pro- 
portion of earthy or alkaline salts, are called saline, although this term is gen- 
erally applied to particularly designate springs containing common salt. 

In some springs carbonic acid is very abundant, and imparts to the water 
an effervescent, sparkling character, like that noticed in the " Seltzer" and 
" Saratoga" waters. 

314. Thermal Springs . — Many mineral springs are of a temperature 
considerably higher than that of the surface of the earth where they make 
their appearance, and not unfrequently discharge boiling water. The major- 
ity of hot springs occur either in the vicinity of volcanoes, or they rise from 
great depths in rocks of the oldest geological periods. With few exceptions, 
they discharge at all times the same quantity of water, and their temperature 
and chemical constituents remain constant. There is evidence to show that 
the temperature of some hot springs has not diminished for upward of a thou- 
sand years. 

315. River -water is less fitted for drinking purposes than spring- 
water, although it often contains a smaller amount of dissolved salts. But 
river-water usually holds in solution or suspension large quantities of or- 
ganic matter of vegetable origin, derived from the surface of the country 
drained by the stream. If the sewerage of large towns situated on its banks 
be allowed to pass into the stream, it is of course less fit for domestic pur- 



Water, however, which is contaminated with animal and vegetable matter, 

Questions. — When are waters termed mineral ? What are chalybeate waters ? What 
are sulphurous, or sulphuretted waters? How may they he recognized? What are 
ealine springs ? What gives to Saratoga and Seltzer waters their sparkle ? What are 
thermal springs ? In what localities are they generally found ? What is said of river- 
water ? Can water purify itself? 



214 INORGANIC CHEMISTRY. 

is endowed with a self-purifying power of the utmost importance. The action 
of the oxygen of the air generates a species of fermentation, whereby the or- 
ganic matters contained in the water become oxydated, deprived of both color 
and odor, and precipitated in part as sediment. The water of the river Thames, 
contaminated with the sewerage of London, is a remarkable illustration of 
this fact. Taken on board ships, it is at first nauseous, but after standing in 
casks for a few days, it becomes sweet and wholesome. 

316. Sea-waters . — The most abundant substance in sea- water is bom- 
mon salt ; next the chloride of magnesium and the sulphate of magnesia, 
which compounds give to the water its saline, bitter taste ; then salts of cal- 
cium, potassium, with traces of iron, iodine, bromine, fluorine, silver, and some 
other of the metals. The specific gravity of sea- water varies slightly in dif- 
ferent locations. The waters of the Baltic and of the Black Sea are less 
salt than the average, while those of the Mediterranean and some portions 
of the Gulf of Mexico, are more so. The whole amount of mineral constitu- 
ents in the waters of the main ocean ranges from 3£ to 4 per cent. 

The soluble earthy matters washed from the land by rains into the rivers, 
and by them carried into the ocean, remain there, since pure water alone 
evaporates from the surface of the ocean. The quantity of saline matter, 
therefore, in the ocean is continually accumulating. It is an error to attrib- 
ute the saltness of the sea to the presence of vast beds of mineral salt ; but 
the sea undoubtedly owes all its salts to washings from the land. The 
streams that have flowed into it for ages have been constantly adding to 
the quantity, until it has acquired its present briny and bitter condition. 
The evidence on this point is most conclusive ; the saline condition of sea- 
water is but an exaggeration of that of all ordinary lakes, rivers, and springs. 
These all contain more or less of the mineral constituents of sea- water, but 
as their waters are continually changing and flowing into the sea, the salts 
in them do not accumulate. 

Again, every lake into which rivers flow, and from which there is no out- 
let except by evaporation, is a salt lake ; and it is extremely curious to ob- 
serve that this condition disappears when an artificial outlet is provided. 
Examples of such lakes are the Dead Sea, the Caspian, the Sea of Aral, 
and the Great Salt Lake of Utah, the saltness of all of which greatly ex- 
ceeds that of the ocean. Thus the waters of the ocean contain from 2 to 
3,000 grains of saline matter in the gallon (70,000 grains) ; those of the Dead 
Sea, in some places, 11,000 grains, and those of the Salt Lake of Utah 
22,000 grains, or nearly one third of their whole weight. In some instances, 
even this last proportion is exceeded. 

317. Relative Fitness of Waters for Use . — Any water 
which contains less than 15 grains of ordinary mineral matter in a gallon is 
considered as comparatively pure, and may be employed for all domestio 



Questions. — What is an illustration of this fact ? What are the mineral constituents 
of sea-water ? Why is the sea salt ? What proof is there respecting the origin of salt 
in the ocean ? What is said of the relative fitness of waters for use ? 



HYDROGEN. 215 

purposes, provided it does not contain too large a proportion of organic 
matter. Water, of which a gallon contains 60 grains of ordinary mineral 
matters, may be still good for drinking, but it is not fit for cooking vege- 
tables or washing linen when it contains 8 grains to the gallon of either 
lime or magnesia. Waters which contain 6 grains of organic matter to the 
gallon are not fit for any domestic use; if this limit is exceeded, they act 
disastrously upon the animal economy, and may occasion dysentery and va- 
rious other maladies. .The presence of magnesia in considerable quantity in 
drinkable waters is undoubtedly injurious; the use of such waters in Swit- 
zerland is supposed to give rise to the frightful diseases known as "goitre" 
and "cretinism."* The disagreeable, earthy taste of certain well-waters in 
most cases, arises from the presence of alumina, held in solution by carbonic 

One of the purest natural waters ever examined is that of the river Loka 
in the north of Sweden, which flows mainly over granitic rocks, upon which 
water produces little impression. It contains only l-20th of a grain (0-0566) 
of solid mineral matter per gallon. Such instances, however, are ver 7 rare- 
but water containing as little as 4 or 5 grains of solid matter to the gallon are 
not unfrequent. The quantity of organic matter in water is always greatest 
in summer, and disappears for the most part when the temperature of the 
water sinks to the freezing-point. Water, by filtration through finely pow- 
dered charcoal, may be almost entirely deprived of organic impurities 

318. Hard and Soft W a t e r s .-Water is familiarly spoken of as 
hard or soft, according to its action on soap. Those waters which contain 
compounds of hme or magnesia occasion a curdling of the soap, as these earths 
produce with the fat of the soap a substance which is not soluble in water 
Soft waters do not contain these earths, and dissolve the soap without difi> 
culty. Many hard waters become softer by boiling, in which case the carbonic 
acid gas which holds the lime and magnesia for the most part in solution Is 
expehed by heat, and the mineral substances are deposited upon the interior 
of the boiler, causing a "fur," « scale, " or incrustation. 

Soft water, or that which is free from dissolved mineral 
matter, possesses a greater solvent power than hard water ■ 
therefore it is most suitable for washing and for the prep- 
aration of solutions. In culinary operations, where the 
object is mainly to soften the texture of animal or veget- 
able substances, or to extract- from them and present in a 

^^treisaswellin gofaeglaads of the neck^d^tin is a variety of idiotcy. 
wS 8 eZ^T H0WmUCh 0r8 ^"°*"*^ 



216 INORGANIC CHEMISTRY. 

liquid form some valuable constituent, as in the prepara- 
tion of soups, tea, coffee, etc., soft water is the Lest. In 
other instances, in which it is desired to cook a substance, 
and not to dissolve it or extract its juice, hard water is 
preferable. To prevent the over-dissolving action of soft 
water in cooking, salt is frequently added, which hardens 
it.* 

319. Much speculation has been occasioned by the circumstance that fresh 
water can generally be obtained by excavating for a few feet or inches on low- 
sandy beaches, or islands in close proximity to the sea, and also by the oc- 
currence, on many of the low coral islands of the Pacific, of fresh water springs 
which ebb with the tide. The explanation of these facts seems to be, that 
the fresh waters are derived from rains, and being lighter than the salt water 
of the ocean, remain suspended in the sands, resting upon the denser water 
beneath. They consequently rise and fall with the motion of the tides. It is 
also true that the water of the ocean, by filtration through sand, is deprived 
in part of its saline constituents. 

320. All ordinary water contains in solution air, and generally a portion of 
carbonic acid gas. The quantity of these gases absorbed by water varies 
with its temperature, and also with the pressure of the atmosphere — cold 
water dissolving and retaining a larger quantity than warm or tepid water. 
When cold waters from springs or fountains arc exposed to warm air, they 
become elevated in temperature, and the gases contained in them escape, ren- 
dering the water flat and insipid. The principal agent in imparting a sparkle 
and freshness to water is atmospheric air, and not carbonic acid gas, as is 
often supposed and taught. 

Air and other gases existing in water may be expelled from it by raising 
the water to a boiling temperature, or by removing the pressure of the 
atmosphere. The presence of air in water may be beautifully illustrated 
by placing a vessel of spring- water beneath tho receiver of an air-pump 



* " These facts explain why it is impossible to correct and restore the flavor in veget- 
ables that have been boiled in soft water by afterward salting them. It is also well 
known that peas and beans do not boil soft in hard water. This is owing to the effect 
which lime exerts in hardening or coagulating a peculiar substance (" casein"), which 
abounds in these seeds. Onions furnish a good example of the influence of quality in 
water. If boiled in pure soft water, they are almost entirely destitute of taste ; though 
when cooked in salted water, they possess, in addition to the pleasan-t saline taste, a pe- 
culiar sweetness and a strong aroma ; and they also contain more soluble matter than 
A/hen cooked in pure water. The salt hinders the solution and evaporation of the soluble 
and flavoring principles." — Youmaii's Household Science. 



Questions. — TIow is the presence of fresh water in close proximity to the sea accounted 
for? What is said of the presence of air in water? Why are waters which have been 
heated flat and insipid? How may air and the gases contained in water bo expelled from 
it ? How may the presence of air in water be demonstrated ? 




HYDROGEN. 217 

(Fig. 105), and gradually exhausting tlio air. As the exhaus- 
tion proceeds, the dissolved air escapes so rapidly as to oc- 
casion tho appearance of ebullition. 

Fishes and other marino animals are dependent upon tho air 
which water contains for their respiration and existence. If 
we place a fish in water which has been entirely deprived of 
air, it is almost immediately suffocated. This fact can, if 
desired, be demonstrated with the aid of an air-pump. The 
quantity of air retained by water, at an altitude of G,000 or 
8,000 feet, owing to a reduced atmospheric pressure, is two-thirds less than 
the usual proportion. Hence it is that fishes can not live in high mountain 
lakes — the amount of air contained in the waters being inadequate for their 
respiration. 

A remarkable evidence of design on the part of Providence in supplying the 
wants of marine animals, which extract the oxygen they require for the sup- 
port of life from the water in which they live, would appear to bo found in tho 
circumstance that water absorbs oxygen and nitrogen — the constituents of air 
— in proportions different from those existing in the atmosphere. Thus, ordinary 
air contains about 21 per cent, of oxygen, but air which exists in water con- 
tains from 30 to 33 per cent. Marine animals, therefore, can obtain more 
easily the necessary supply of oxygen from air which contains one-third of 
this gas, than from air containing but one-fifth. 

It has also been recently discovered by Dr. Hayes, that the water of the 
ocean contains more oxygen near its surfaco than at a depth of one or two 
hundred feet. This fact has probably some connection with the comparative 
scarcity of animal life at great depths. 

When water is in contact with an atmosphere of mixed gases, it dissolves 
of each a quantity precisely equal to that which it would have dissolved if in 
contact with an atmosphere of this gas alone. 

Absolutely puro water can only bo obtained by repeated distillations in 
clean vessels of hard glass. 

321. Solvent Properties of Water.— The solvent prop- 
erties of water far exceed those of any known liquid . 

Most bodies are more soluble in hot than in cold water, the solubility in- 
creasing with the temperature. Among tho few exceptions to this rule may 
be mentioned common salt, the solubility of which is nearly the same at all 
temperatures, and lime, which is more soluble in cold than in hot water. 

322. Chemical Properties of Water.— Water is the 
perfection of a neutral substance, and enters into combi- 



Qtjkstionb.— What relation does air in water sustain to animal life? What are illus- 
trations? What peculiarity characterizes the air contained in water? What is the con- 
dition of air at the surface and at the bottom of the ocean ? In what manner does water 
absorb different gases ? How may absolutely pure water be obtained ? What is said of 
the solvent action of water in general ? What of the chemical properties of water ? 

19 



218 INOKGANIC CHEMISTRY. 

nation most extensively with acids, bases, with a large 
proportion of the salts, and, in short, with most bodies 
which contain oxygen. 

A compound of water, in definite proportions with some 
other substance, is termed a hydrate ; and a body entirely 
free from water in combination is said to be anhydrous. 

When a salt simply dissolves in water, the act of solution is uniformly at- 
tended with the production of cold ; but when water* chemically combines 
with a salt, or forms a definite hydrate, the formation is always attended with 
heat ; this circumstance indicates an essential difference between solution in 
water and chemical combination with water. 

" Slacked lime" is a familiar example of a hydrate. When water is added 
to quick lime, it rapidly combines with it, producing great heat r and a chem- 
ical compound results, which is a "hydrate of lime." When water unites 
with potash and soda under the same circumstances the chemical union be- 
tween the two substances is so strong, that no amount of heat alone is sufficient 
to separate them. So also when an acid has once been allowed to combine 
with water the. entire separation of the two is seldom practicable, unless some 
base, for which the acid has a greater affinity than for water, be presented • 
in such a case the base displaces the water, and its expulsion by heat is then 
easily effected. For example, suppose that sulphuric acid has been freely 
diluted with water: upon the application of heat, the water at first passes 
off readily, leaving the less volatile acid behind. By degrees, however, it 
becomes necessary to increase the temperature in order to continue the dis- 
tillation of the water, and at last the acid begins to evaporate also, and finally 
no further separation can be effected, as when the temperature rises to about 
620° ¥., both water and acid distil over together. It is found on analyzing 
the liquid when it has reached this point, that the liquid contains one equiv< 
alent of acid and one of water, its composition being represented by the sym- 
bols SO3, HO. If to this concentrated acid an equivalent of potash be added, 
the water is easily expelled, and an equivalent of anhydrous sulphate of 
potash (KO, S0 3 ) remains. Water, when it thus supplies the place of a base 
in combination with acids, is called basic water. 

323. Peroxyd, or Binoxyd of Hydrogen, sometimes 
called oxygenated water, was discovered by Thenard, in 
1818. It contains twice as much oxygen as water, and is 
a body characterized by most remarkable properties. 



* For explanation of water, of crystallization, deliquescence, efflorescence, etc., see §§ 
64, 65, 66, 67, pp. 48, 49. 

Questions — What is a hydrate ? When is a body said to be anhydrous ? What fact 
illustrates the difference between a solution in, and a combination with, water ? What 
are illustrations of water in combination ? When is water said tc> be basic ? What is 
6aid of the second oxyd of hydrogen ? 



NITROGEN. 219 

It is formed by decomposing peroxyd of barium by sulphuric or hydroflu- 
oric acids. The process, however, is most difficult and complicated. 

Peroxyd of Hydrogen is a syrupy liquid, of specific gravity 1*45, transparent, 
colorless, and almost inodorous, but possessed of a most nauseous and astrin- 
gent taste. Although it differs from water only in containing an additional 
equivalent of oxygen, it is a powerful bleaching agent ; and when applied to 
the skin for any length of time, whitens and destroys its texture. It can be 
preserved only at a temperature below 59° F. Heat rapidly decomposes it 
into water and oxygen gas, and at a temperature of 212° F., the evolution 
of gas is so rapid as to occasion an explosion. The mere contact of carbon, 
and of many of the metals and metallic oxyds also occasions its instantaneous 
decomposition, accompanied by an explosion and evolution of light. 

The known properties of this substance render it highly probable that it 
would prove most valuable in its application to art — as a bleaching and oxyd- 
izing agent. The expense and difficulty attending its preparation have, how- 
ever, thus far prevented its employment for any practical purpose. 

SECTION IV. 

NITROGEN, OR AZOTE. 
Equivalent 14. Symbol N. Density 0-971. 

324. History. — Nitrogen was first recognized as a dis- 
tinct element by Dr. Kutherford, of England, in 17T2. 

— Its-name is derived from the Greek vcrpov, niter, and yevvao), I form (the 
generator of niter). Lavoisier, from its inability to support life, termed it 
Azote (from a privative, and ^urj, life). 

325. Natural History. — Nitrogen is one of the most 
abundant of the elements. 

As a constituent of the inorganic kingdom of nature,, we find it in the at- 
mosphere, of which it constitutes four-fifths; in ammonia; in bituminous coal ; 
in the well-known salts, nitrate of potash and nitrate of soda (niter, saltpeter), 
and in many other mineral compounds. In the organic kingdom, nitrogen 
especially characterizes animal, in contradistinction to vegetable products; 
nevertheless it is found in the latter, but in small quantities. One-fifth of the 
weight of the dried flesh of animals is nitrogen. The plants which contain it 
in greatest quantity belong to the orders cruciferee (turnips, cabbages, horse- 
radish, mustard), and fungacese (mushrooms, etc.). Inasmuch as animals con- 
tain so much nitrogen, and vegetables so little, Berzelius imagined that nitro- 
gen was generated in some unknown way by the animal functions. This 
idea, however, has been opposed by Liebig, who, with the majority of chemists, 
believes that the nitrogen existing in plants, upon which all animals directly 

Questions. — How is it formed ? What are its properties ? Has the peroxyd of hydro- 
gen been applied to any practical use ? What is the history of nitrogen ? What is said 
of its distribution in nature ? What plants contain it in greatest abundance? " 



220 INORGANIC CHEMISTRY. 

or indirectly feed, is sufficient to account for the large quantities of that element 
locked up in the tissues of animals. It is yet, however, one of the great 
unsettled questions in chemistry, and also in agriculture, whence plants derive 
their nitrogen ; — whether from the soil (from manures and decaying organic 
matter), or from the air directly, or from the ammonia contained in the air. 

326. 'Preparation. — The usual methods of obtaining a 
supply of nitrogen for the purpose of experiment are based 
upon the removal of oxygen from atmospheric air — leaving 
the nitrogen isolated or alone. 

The simplest plan consists in placing a few fragments of phosphorus in a 
little metallic or porcelain cup, which is floated upon the surface of the water 
Ei'G- 106 of a pneumatic trough. The phosphorus is ignited, and 

a glass jar or receiver, filled with air, is then inverted 
over it, with its lip in the water. (See Fig. 106.) The 
phosphorus burns at the expense of the oxygen in the 
confined air, and by reason of its great affinity for oxy- 
gen, it combines with every portion of this element con- 
tained in the receiver, leaving the nitrogen compara- 
tively pure. As the combustion proceeds, the water of 
the pneumatic trough gradually rises in the jar to supply 
the place of the consumed oxygen. The product of the union of the phosphorus 
and the oxygen is phosphoric acid, which at first pervades the receiver as a 
dense white vapor, but after a little time is absorbed by the water. 

Alcohol, ignited in a little cup, may be substituted in the place of phos- 
phorus in this experiment, but it does not consume the oxygen entirely, and 
produces also a certain quantity of carbonic acid. 

The removal of oxygen from the air may also be effected more slowly in 
various ways. A stick of phosphorus introduced into a jar of air standing 
over water, will slowly absorb the oxygen, and in two or three days about 
four fifths of the original bulk of the air, consisting of nitrogen nearly pure, 
will be left. Moistened iron filings produce a similar result, the metal gra- 
dually becoming oxydized, as is seen by the rusty appearance which it as- 
sumes. 

Nitrogen may also be obtained by conducting chlorine gas into a solution 
of ammonia ;* by exposing muscle (flesh) to the action of nitric acid in a re- 
tort to which heat is applied ; and in a state of great purity by passing a cur- 
rent of air through a tube containing copper turnings heated to redness ; the 
oxygen in this experiment being entirely absorbed by the copper to form 
oxyd of copper, while the nitrogen passes off. 

321. Properties . — Nitrogen is a colorless, tasteless, and odorless gas, 




This experiment is a somewhat dangerous one. (See chloride of nitrogen.) 

x . _____ 

Questions. — Is it known in what manner plants obtain their nitrogen ? How is nitro- 
gen obtained ? Enumerate some of the methods employed ? What are the physical prop- 
erties of nitrogen ? 



NITROGEN. 221 

which as yet has resisted every effort to liquefy it. It is somewhat lighter ^ 
than atmospheric air, having a specific gravity of 0-971 (air = TOO). 

One of the most distinguishing characteristics of nitrogen is its inertness, or 
"sluggishness;" it being, so far as chemical properties are concerned, in strik- 
ing contrast with oxygen, which is one of the most energetic of the elements. 
It is neither acid or alkaline, and neither supports combustion, or burns. A 
burning taper is instantly extinguished in this gas, and an animal immersed 
in it quickly perishes ; not because the gas is injurious, but for want of oxy- 
gen, which is required for both respiration and combustion. It, however, 
enters into the lungs with every act of inspiration ; is a constituent of our most 
nutritious food, and a necessary component of the animal frame. 

Nitrogen does not unite directly with any other single element; but its 
combination with the various elements all result from the agency "of indirect, 
oblique, or circuitous processes, which conditions being accorded, we fre- 
quently have whole classes of substances springing into existence ; whereas, 
in the case of hydrogen, the combining tendency is satisfied with the forma- 
tion of only one or two compounds." — Faraday. 

A striking illustration of the non-combining properties of nitrogen, is found 
in the fact, that no less than six tons of air pass through an average-sized 
iron blast furnace every hour, during which transit the oxygen part of the air 
is most active in forming combinations, while the nitrogen, although subjected 
to precisely similar conditions of heat and contact, emerges as it entered, un- 
combined. 

328. Instability of Nitrogen in Composition , — Nitro- 
gen, of all ponderable substances, appears to have the greatest affinity for 
heat, and when in combination, constantly tends to unite with it, and resume 
its elementary condition of a gas. In consequence of this, and also by reason 
of its slight affinity for the other elements, the compounds of nitrogen are re- 
markably unstable. Many of them are decomposed with extreme suddenness 
by the slightest causes — the nitrogen being disengaged in the gaseous form, 
and often producing most violent explosions. Most of the explosive sub^ 
stances known are compounds containing nitrogen as an essential constitu* 
ent ; as, for example, gunpowder, gun-cotton, fulminating mercury (percussion-, 
cap powder), fulminating silver, etc. , 

A substance known as the iodide of nitrogen strikingly illustrates oy its 
mode of preparation the peculiarly indirect processes demanded by nitrogen 
for calling its powers of combination into play, and by its character when 
formed, the instability of the same element when forced into union with an- 
other body. Iodide of nitrogen is a simple compound of iodine and nitrogen. 
These two elements when mixed together directly manifest no disposition ta 
unite, and may be preserved in contact unchanged for an indefinite period. 
But when nitrogen is brought in contact with iodine by an indirect process, 



Questions. — What is one of the most distinguishing characteristics of nitrogen ? Illus. 
trate this. What is said of the combinations of nitrogen ? What circumstance illustrates 
the non-combining properties of nitrogen ? What peculiar^ has nitrogen in composition ? 



222 INOKGANIC CHEMISTRY. 

as when a strong solution of ammonia is mingled in a glass vessel with a satu- 
rated solution of iodine in alcohol, combination almost immediately ensues, 
and a black powder, iodide of nitrogen, is formed. This, after standing for 
about a quarter of an hour, is separated from the liquid by filtration, washed 
in the filter with pure water, and dried by exposure to the air in a cool 
situation. As thus prepared, it is one of the most explosive substances 
known, the nitrogen being held by so slight an excess of force, that the merest 
friction between the particles of the compound is sufficient to shatter it into 
its elements. This result may be illustrated by a variety of experiments. A 
small quantity projected upon water explodes the instant it strikes its surface ; 
the same result attends the dropping of a fragment from a slight elevation 
upon a hard surface, or by placing a small quantity upon one end of a counter 
and striking the other end with a hammer.* 

Nitrogen, in some mysterious way, appears to be associated with all the 
higher forms of animal existence. The blood, the muscle, the brain, the 
nerves of animals, all contain it in large quantity, and these substances, of 
all organic compounds, are the ones most susceptible of decomposition. 

Organic bodies which contain a large amount of nitrogen, generally emit a 
most offensive odor when they decay. The odor occasioned by the putre- 
faction of a dead human body, which is rich in nitrogen, is one of the most 
offensive in nature. Plants which contain this element in considerable quan- 
tity, as the cabbage and mushroom, putrefy with an animal odor. Sub- 
stances containing nitrogen also emit an offensive and peculiar odor when 
burned; as for example, the smell of burnt hair, leather, flesh, bones, etc. 
This odor may be regarded as an invariable test of the presence of nitro- 

Nitrogen constitutes an essential element of many of the most valuable 
[ and potent medicines, as quinia and morphia, and also of some of the most 
\ dangerous poisons, as prussic acid and strychnia. 
^ A suspicion has always existed that nitrogen may be a compound body. 
One circumstance which has led to this idea, is its demeanor as respects elec- 
tricity. Most of the binary compounds yield up their elements in obedience 
to the direction of this force, but electricity determines no liberation of nitro- 
a gen from any of its combinations. All attempts, however, to decompose it 
have failed, and its position among the elements must therefore remain undis- 
puted. 

* Iodide of nitrogen, prepared as above, is not liable to explode while moist, and in 
very small quantities may be used without danger. For the purpose of experiment mi- 
nute portions of it should bo taken upon the point of a penknife blade, or upon the end 
of a glass rod. 

Questions. — Into what class of compounds does it particularly enter as a constituent? 
"What characteristics of nitrogen are illustrated by the compound, iodide of nitrogen ? 
What is said of nitrogen in the animal system ? What circumstance characterizes the 
decay of bodies rich in nitrogen? What is one of the tests of the presence of nitrogen in 
» body ? What is said of the elementary character of nitrogen ? 



NITROGEN. 223 

THE ATMOSPHERE. 

329. History . — The air was formerly supposed to be an element, but 
was not altogether regarded in the light of a material substance. The posi- 
tion which it held in the old systems of philosophy was similar to that as- 
signed to light, heat, and electricity in some systems of the present day — a 
fluid substance without weight, form, color, or, in short, any of the ordinary 
attributes of matter. 

It was not until 1613 that it was even suspected that airs, other than at- 
mospheric air, might have an existence. About that time Robert Boyle, an 
English chemist, maintained "that some solid bodies do, in certain circum- 
stances, as when heated, throw off artificial airs resembling atmospheric air 
in thinness and elasticity, as well as in dryness and permanency, but differing 
from it he could not well tell how." 

In the beginning of the 17th century the workmen in certain German 
mines were molested (as miners still are) by certain agencies, some of which 
were liable to suffocate them silently but summarily (carbonic acid), while 
others burned, or exploding, blew them into fragments, (fire-damp, carburetted 
hydrogen). Von Helmont, the old alchemist, explained these phenomena by 
referring them to the agency of spirits, the guardians of the mineral treas- 
ures, whom he called geists (ghosts). From this originated the English word 
gas, which is still employed to designate aeriform substances. 

Torricelli, a pupil of Galileo, first proved, in 1643, that atmospheric air pos- 
sessed weight ; and one hundred and fourteen years afterward, or in 1757, 
Joseph Black, a Scotch chemist of Edinburgh, first discovered and collected 
in a separate state a gas other than atmospheric air. He ascertained that 
limestone (chalk, marble, or oyster-shells) when burned in a kiln, or 
heated with a strong acid, parts with a kind of air in which no animal can 
breath and live. This gas (which we now call carbonic acid) Black termed 
fixed air, because it was imprisoned in the rock until the furnace or the acid 
extricated it from its fixture. 

This discovery wa3 one of the greatest that has ever been made in chem- 
istry, since it for the first time clearly proved that there may exist different 
kinds of airy matter (just as there are different kinds of solid and liquid sub- 
stances), differing as much from the gas of the atmosphere as oil or sulphuric 
acid differ from water, or as slate or marble from sandstone. 

Shortly after this discovery by Black, Dr. Priestley devised the pneumatic 
trough (once known as the Priestleyan trough) and by so doing rendered easy 
the collection and handling of gaseous substances. He also discovered and 
isolated nine different gases, and among them oxygen. Scheele, working in 
an obscure Swedish town, with no other apparatus but phials and bladders, 
about the same time added two or three more to the list. Discoveries of the 

Questions — How was air regarded by the ancients? When was the existence of sepa- 
rate gases first suspected ? What was the origin of the term "gas ?" Who first demon- 
strated the weight of air ? Who first collected and recognized a separate gas ? What 
was the nature of Black's discovery ? What is said of the importance of this discovery ? 
What discoveries succeeded that made hy Black ? 



224 



INORGANIC CHEMISTRY 



same kind then took place in rapid succession all over Europe. Cavendish 
followed with hydrogen, Rutherford with nitrogen, while Lavoisier overthrew 
the great old doctrine of the elementary nature of air, by proving that it con- 
sisted of two gases mingled in unequal proportions.* 

Within a comparatively recent period it has been admitted as a fundamental 
principle in physical science, that " gases are merely the steams of liquids 
which boil at immensely low points of temperature, these liquids being the 
liquefactions of solid bodies which melt at temperatures lower still, and that 
therefore there may be no end to the number of the kinds of gaseous mat- 
ter, precisely as there is no known limit to the vast variety of liquids and 
solids." 

330. Atmospheric Air consists essentially of nitrogen 
and oxygen mixed together in the proportion of four fifths 
by volume of the former to one fifth of the latter. 

More correctly, the composition of air which has been freed from the pres- 
ence of all foreign ingredients may be represented by measure and weight as 
follows : — 

By weight. 

Nitrogen 76-90 

Oxygen 23-10 

10000 100-00 



By measure. 
79-10 
20-90 



In addition to oxygen and nitrogen, the atmosphere always contains small 
and variable proportions of carbonic acid gas and aqueous vapor ; and very 
often, minute quantities of ammonia, nitric acid, the aroma of flowers, and va- 
rious other organic and inorganic products ; — in short, as the sea contains 
traces of almost every thing that is soluble, so the air contains traces of almost 
every thing that is volatile. 

The oxygen and nitrogen existing in the air are merely intermingled, and 
not chemically combined with each other; but their relative proportions 
never vary. This has been proved by the analysis of air collected upon the 
summit of Mount Blanc, and upon the Andes ; at an elevation of 21,000 feet 
by Guy Lussac in a balloon ; over marshes ; in hospitals ; over deserts ; and 
at the bottom of the deepest mines. 

The quantity of carbonic acid, on the contrary, being much influenced by 
local causes, varies considerably. The average quantity is 4.9 volumes in 
10,000 of air, but is observed to vary from 6.2 as a maximum to 3.7 as a 
minimum in 10,000 volumes. Its proportion near the surface of the earth is 



* The experiment by which Lavoisier arrived at this result is described under the 
head of Combustion. ' 



Questions.— What is now understood to be the true nature of gases? What is the 
composition of atmospheric air ? In what condition do oxygen and nitrogen exist in the 
air ? Are the proportions of those two gases variable ? What is the proportion of car- 
bonic acid in the air ? Under what circumstances does it vary ? 



NITROGEN. 225 

greater in summer than in winter, and during night than during day. It is 
also rather more abundant in elevated situations, as on the summits of high 
mountains, than in plains ; this is probably owing to an absorption of tho gas 
near the surface of the earth by plant3 and moist surfaces. An enormous 
quantity of carbonic acid gas is discharged from the elevated cones of the vol- 
canoes of America, which may partially account for the high proportion of 
this gas in the upper regions of the atmosphere. The gas emitted from the 
volcanoes of the Old "World is said to be principally nitrogen. 

The quantity of watery vapor contained in the air varies with the temper- 
ature (§ 141, page 92). It seldom forms more than l-60th or less than 
l-200th of the bulk of the air. 

Notwithstanding the difference in density between each of the principal 
constituents of the atmosphere — nitrogen, oxygen, carbonic acid, and the 
vapor of water — and notwithstanding, also, the absence of any chemical 
union between them, they are always, through the action of the law of the 
diffusion of gases (§ 51, page 39), found uniformly mingled together. The 
operations, also, of combustion, respiration, vegetation, and the like, continu- 
ally going on upon the earth's surface, remove great quantities of oxygen 
from the air, and substitute a variety of other gases, the principal of which is 
carbonic acid ; yet so beautifully adjusted i3 the balance of chemical action 
in nature, that no perceptible change in the composition of the atmosphere 
has been observed since accurate experiment on the subject was first com- 
menced. 

Ammonia seems to be an almost constant constituent of the atmosphere in 
exceedingly minute quantity. Recent most-carefully conducted experiments 
by M. Yille of France, fix the average quantity as i volume in 28,000,000 of 
air. Other experimenters have deduced a much greater result. 

Nitric acid may be usually detected in the rain-water obtained during a 
thunder-shower. It is supposed to be formed by the union of the oxygen, 
nitrogen, and aqueous vapor of the air, through the agency of electricity. 

Organic matter of some kind is almost always present in the atmosphere ; 
but it not unfrequently happens that chemical tests fail to detect it, when the 
sense of smell and a peculiar effect upon the human constitution give abun- 
dant evidence of its presence. This is especially true of the odoriferous mat- 
ters of flowers, and the miasmata of marshes. Dew collected over rice-fields 
often contains so much decomposing organic matter, as to become putrid after 
standing for a short time. Exposure to the night air of these localities in the 
hot season, invariably produces in the Caucasian race, malignant and almost 
incurable fevers. 

The principal office which nitrogen appears to sustain in the atmosphere, 
is that of a diluent of the oxygen. If the quantity of oxygen in the air was 
increased much beyond its present proportion, the inflammability of most sub- 

Qttestio^s. — Ho-w does the quantity of aqueous vapor vary? What is said of the uni- 
formity of the condition of the atmosphere ? What of the ammonia of the atmosphere ? 
What of nitric acid ? What of organic matter ? What office does nitrogen appear to 
sustain in the atmosphere? 

10* 



? 



226 



INORGANIC CHEMISTRY. 



stances ■would be greatly augmented; and the functions of life would be 
called into such rapid action as to soon exhaust the powers of the system. 
Nitrogen being the most indifferent of all substances, and wanting in any 
poisonous qualities, dilutes the too active oxygen, and prolongs its action 
upon the system, in the same way as water dilutes and diminishes the stim- 
ulating action of spirituous liquors. Eecent researches have also rendered it 
probable that the nitrogen of the air discharges an important office in respir- 
ation, by preserving the volume and tension of the cells and extreme tube3 
of the lungs. — Prof. Moultrie. 

Oxygen is strikingly magnetic ; nitrogen is singularly the reverse ; and 
the atmosphere, a mixture of both, is nearly neutral as respects magnetism in 
all its relations to matter. 

Another illustration of the adaptation of nitrogen to its atmospheric func- 
tions is to be found in its specific gravity, or density, which is nearly the 
same as that of its associated oxygen. Had there been any great difference 
in this respect, the tendency of the two gases would have been toward sep- 
aration, and this, notwithstanding the influence of the law of diffusion. 
Again, as the atmosphere is now constituted, there exists a permanency of 
the pitch of sound : any tone being once generated, remains the same tone 
until it dies away. Its degree of loudness alters in proportion to the distance 
of the listener from the place where it originated, but its pitch — never. If 
the specific gravity of oxygen and nitrogen had, however, been widely dis- 
similar, there would have been a difference. No permanency of tone could 
then have been depended on, and the pitch of every original note would have 



Fig. 107. 




varied continually. "All the studied ar- 
rangement of defined notes, which constitutes 
the art of music, would have been lost to us 
forever, had we been enveloped in such an 
atmosphere." These facts may be illustrated 
by striking a sonorous body in a receiver 
containing air, and afterward in one contain- 
ing hydrogen, which is much lighter than 
air. (See Fig. 107.) The experiment may be 
varied by causing a tuning-fork in the key 
to vibrate over a small glass jar, which, 
when made to resound, emits the same note, 
and is therefore in union with the fork. If 
the jar be now filled with hydrogen, and 
inverted, to prevent the escape of gas, and 
the fork be again caused to vibrate opposite 
its mouth, the unison is destroyed, and the 
sound is no longer responsive to the note C. 



Questions. — What is said of the magnetic condition of the atmosphere ? How does the 
specific gravity of nitrogen adapt it to its condition in the atmosphere ? What experi- 
ments illustrate this ? 



NITROGEN 



227 



Fig. 108. 




331. Analysis of Air . — The proportions of oxygen and nitrogen in 
the atmosphere are determined by withdrawing the oxygen from a measured 
portion of perfectly dry air, through the agency of va- 
rious substances which absorb it. (See § 326, page 220.) 
A stick of phosphorus introduced into a known measure 
of air in a graduated tube, the open end of which is be- 
neath the surface of water (see Fig. 108), effects a com- 
plete absorption of the oxygen in about 24 hours. 
The water rising in the tube indicates a diminution of 
one fifth in the volume of the air — or what is the same 
thing, a withdrawal of from 20 to 21 per cent, of oxygen. 
The carbonic acid, aqueous vapor, ammonia, and the 
occasional constituents of the atmosphere, are deter- 
mined by passing a measured quantity of air through 
receptacles containing materials which absorb and retain 
them. 

The arrangement by which this can be best effected is 
called an Aspirator. It consists simply of a tight cask of 
a known capacity, filled with water, and provided at 

-p IG 1Q9 the base with a stop-cock. 

At the top of the cask, a 
tube, or series of tubes, or 
other vessels are fitted, as 
is represented in Fig. 109 ; 
one filled, for example, with 
pumice stone drenched with 
strong sulphuric acid, and 
another with caustic potash. 
When the cock of the vessel is opened, and the water allowed to flow out, its 
place is supplied by an equal volume of air, which flows in through the 
tubes. The sulphuric acid • absorbs all the moisture contained in the air - 
which flows over it, and the potash all the carbonic acid. The quantity 
of air that passes through the tubes is known by the quantity of water 
that flows out of the cask, while the increased weight of the separate 
tubes gives the total amount of moisture and carbonic acid contained in such 
quantity. >— J- 

332. Compounds of Nitrogen and Oxygen. — Nitrogen 
unites with oxygen to form five distinct compounds, con- 
taining, respectively, 1, 2, 3, 4, and 5 equivalents of oxy- 
gen, with 1 of nitrogen. 

Their names and chemical constitution are thus expressed : 




Questions. — How is air analyzed ? How are the carbonic acid and aqueous vapor of the 
air determined ? "What is an aspirator ? How many compounds of oxygen and nitrogen 
exist ? 



228 



INOKGANIC CHEMISTRY. 



Composed by weight of 

Symbol. , ■ „ 

Protoxyd of nitrogen (nitrous oxyd) NO 14 nitrogen + 8 oxygen. 

Deutoxyd of nitrogen (nitric oxyd) NO-2 1-1 " +16 " 

Nitrous acid NO3 14 " + 24 " 

Hyponitric acid (peroxyd of nitrogen).. NO4 14 " +32 " 

Nitric acid NOs 14 " +40 " 

Three of these compounds are acids ; and all of them are endowed with 
qualities so marked, so powerful, and so well defined, that the original attri- 
butes of their elements are entirely lost. 

333. Nitric Acid, N0 5 . — Nitric acid is the most import- 
ant of all the combinations of nitrogen and oxygen, and is 
the source from whence most of the compounds of nitrogen 
are generally obtained. 

334. History . — It was known to the alchemists, but its true composition 
was first determined by Cavendish in 1785. The name formerly applied to it, 
and which is still used to some extent, was aquafortis. 

335. Distribution . — Nitric acid occurs in nature usually in combina- 
tion with potash, soda, or lime in the soil, especially in tropical countries, as 
in some parts of India and Peru. The compound formed with potash consti- 
tutes the nitre or saltpeter of commerce. In the desert of Atacama, in Chili 
and Peru, it exists in vast quantities combined with soda, forming nitrate of 
soda, which salt is also caUed " Chilian saltpetre," or cubic niter. Nitric acid, 
as already stated, also exists occasionally in the atmosphere, especially during 
and after the occurrence of tbunder-storms. 

336. Preparation . — When nitrogen is mixed with twelve or fourteen 
times its bulk of hydrogen, and a jet of the mixed gas is allowed to burn in 
air, or in oxygen, the water formed has a sour taste and an acid reaction from 
the formation of a small quantity of nitric acid. In this case the nitrogen 
burns by reason of the great heat developed during the combustion of the hy- 
drogen, and the nitric acid combines at once with the water formed, which 
last substance, in some way by its presence, aids the operation. It was from 
noticing the acidity of water formed by the combustion of hydrogen in air, 
that Cavendish was led to institute an investigation which terminated in the 
discovery of nitric acid. He mixed together the two gases, oxygen and ni- 
trogen, in a close tube, over a solution of potash, and then caused them slowly 
to combine by passing a series of electric sparks through the mixture for sev- 
eral successive days. At the conclusion of the experiment, the glass contained 
nitrate of potash (saltpeter). A similar result will be produced if a number 
of sparks be passed from an electrical machine, through air between two- 
metallic points, over moistened litmus paper : a red spot will be produced 
upon the paper, owing to the formation of nitric acid in minute quantity by 
the combination of oxygen with nitrogen. 

Questions. — Give the series. What is said of nitric acid? What of its history? 
What of its distribution in nature ? How may nitric acid he fowned ? What circum- 
stances led to its discovery ? 



NITROGEN 



229 




For all practical purposes, nitric acid is always obtained by heating one of 
the natural compounds of nitric acid with potash or soda in a retort, with an 
equal weight of strong sulphuric acid. The nitric acid is displaced by the 
sulphuric acid, and distils over, being much more volatile than the sulphuric 
acid. 

This process may be easily Fig. 110. 

illustrated experimentally 
by introducing into a glass 
retort, Fig. 110, equal 
weights of powdered salt- 
peter and strong sulphuric 
acid. The retort should be 
supported upon a thin layer 
of sand contained in a tin 
or sheet-iron vessel (tech- 
nically termed a sand-bath), 

and the heat supplied by an ordinary alcohol-lamp ; a flask cooled by a wet 
cloth, or placed in a vessel of cold water, is adapted to the retort, and serves 
as a receiver. During the distillation red fumes appear in the retort, arising 
from a partial decomposition of the nitric acid formed, and a production of 
some of the lower oxyds of nitrogen.* 

On a large scale, iron retorts coated on the inside with fire-clay are em- 
ployed. The chemical reaction involved in this process may be represented 
as follows : 

KO, N0 5 -f-S0 3 =KO, S03+N0 5 . 

Or sulphuric acid and nitrate of potash give nitric acid and sulphate of 
potash. .m*»*e~^ 

331. Properties . — Nitric acid, when pure and in a concentrated state, 
is a colorless, limpid, fuming liquid, powerfully corrosive and intensely acid. 
As found in commerce, it is never pure, and is of a golden-yellow color. It 
is the highest oxyd of nitrogen known to exist, and has a specific gravity 
of 1*52 (water = 1). Anhydrous nitric acid, or nitric acid without water 
combined with it, can be prepared by a most carefully conducted chemical 
process ; but under all ordinary circumstances it contains a certain proportion 
of water ; its constitution being represented by the formula NOs, HO. In the 
most concentrated state in which it can be used, it consists of 54 parts real 
acid and 9 of water. 

Nitric acid is very readily decomposed, and mere distillation causes a par- 
tial decomposition. Exposure to light produces a similar result, oxygen and 



* The retort generally breaks at the conclusion of this process from the crystallization 
of the sulphate of potash formed, hut it may be saved by adding to it, when partially 
cooled, a small quantity of warm water. 



Questions. — How is it practically prepared ? What is the chemical reaction involved 
in the practical production of nitaic acid ? "What are the properties of nitric acid ? Does 
it exist apart from water ? Is nitric acid easily decomposed ? What effect has light upon it ? 



230 INORGANIC CHEMISTRY. 

some of the lower oxygen compounds of nitrogen, which produce discolora- 
tion, being evolved — sometimes in quantity sufficient to expel the stopper of 
a bottle. In its concentrated form it begins to boil at 184° P., and freezes 
at about — 40° P. 

338. Chemical Action of Nitric Acid , — Nitric acid is one of 
the very strongest acids, and ranks next to sulphuric acid. It attacks most 
inorganic substances, and all living tissues. It turns wool, feathers, the skin, 
and all animal matters containing albumen, a bright yellow color ; the orange 
patterns upon woolen table-cloths are produced by means of it. In medicine 
it is not unfrequently used as a powerful cauterizing agent. 

The effect of concentrated nitric acid upon animal tissues may be illus- 
trated by applying a drop to a piece of parchment, which immediately be- 
comes stained and shrivelled.* 

The action of nitric acid on vegetable colors may also be illustrated by the 
following experiment : — Color some water blue in a test tube with a solution 
of indigo, and add to it on boiling, a drop of nitric acid ; the blue color will 
almost immediately disappear. f 

Nitric acid, when in its state of highest concentration, exerts no violent 
action upon certain organic substances, such as woody fibers, starch, etc., but 
unites with them to form most singular compounds. Cotton fibers immersed 
in it for a few moments and then carefully washed in water, are converted 
into a violently explosive substance. (See gun-cotton.) 

Commercial nitric acid will completely dissolve, in the cold and without 
odor, a little less than its own weight of flesh and bone (beef), in a space of 
time varying from three to five hours. The action of nitric acid, however, 
upon organic substances and the metals is exceedingly different at different 
degrees of concentration. 

Nitric acid very readily parts with a portion of its oxygen to the metals 
and to combustible bodies, and is therefore one of the principal agents made 
use of in chemistry for causing such substances to assume, or pass into a state 
of oxydation. 

If nitric acid be dropped upon hot finely powdered charcoal, the charcoal 
burns vividly ; if mixed with a little oil of vitriol, and poured upon oil of tur- 
pentine, it occasions an explosive combustion. Phosphorus is readily ignited 



* It is an extraordinary, very cruel, and too common experiment made by physiologists 
to illustrate what they are pleased to call a power of vital contractility under the influ- 
ence of a stimulus, by touching with a glass rod dipped in nitric acid, the heart of a Irving 
rabbit. In an instant the heart shrivels and contracts to one third its original size. — 
Faeaday. 

t Indigo solution — a most useful chemical reagent — may be easily formed by pulvcr. 
izing a small quantity of indigo, and forming a thin paste of it with strong sulphuric 
acid. After a few days add water, and a deep blue liquid, solution of indigo, is obtained. 

Questions. — What are its freezing and boiling points ? "What is said of its chemical 
character ? How may the action of nitric acid upon animal tissues be illustrated ? How 
its action upon vegetable colors ? How upon vegetable fibers ? How is nitric acid able 
to produce oxydation ? 



N ITS, GEN. 231 

by throwing it upon strong nitric acid. This experiment is a somewhat haz- 
ardous one, and particles of phosphorus scarcely larger than the head of a pin 
should alone be employed. 

339. The Action of Nitric Acid upon the Metals is in- 
structive, and serves to illustrate the manner in which metallic bodies com- 
bine with the acids generally. The metals will enter into direct combination 
with many of the simple non-metallic bodies. Thus antimony will unite with 
chlorine, iron with oxygen, and copper with sulphur ; but no metal will unite 
directly with an acid. In order that combination between them should oc- 
cur, it is necessary that the metal should be in the form of an oxyd. This 
oxydation may, however, be effected at the same time that the acid is pre- 
sented to the metal, and the formation of the oxyd and its solution in the " 
acid may appear to occur simultaneously. Zinc, for example, does not unite 
as zinc with sulphuric acid ; but when this metal is placed in dilute sulphuric 
acid, the oxygen is supplied from the water contained in it, which, is de- 
composed ; — oxyd of zinc is produced and is immediately dissolved by the 
acid, whilst the hydrogen escapes in the gaseous form. "When a metal, 
such as copper or silver, is dissolved by nitric acid, a preliminary oxydation 
is equally necessary ; but owing to the facility with which nitric acid is de- 
composed, this oxydation is usually effected by depriving the acid of a por- 
tion of its oxygen, it being more readily decomposed than water. When this 
takes place, a part of the products of the decomposition of the acid escapes 
into the air in the form of deep red fumes (see hyponitric acid), while the 
compound of the metal with oxygen dissolves in another portion of the acid 
which has not undergone decomposition. It is through this peculiar action 
of nitric acid that it is rendered a most ready and powerful solvent of most 
of the metals. — Miller. 

340. Salts of Nitric Acid , — The salts formed by the union of 
nitric acid with the bases are termed nitrates, and are especially remarkable 
for the circumstance that they are soluble in water. "When the nitrates are 
projected upon glowing coals they are decomposed ; and by reason of the es- 
cape of oxygen, they deflagrate, or burn furiously with scintillations. If dis- 
solved in water, and paper be moistened with the solution, allowed to dry, 
and then burned, the peculiar combustion characteristic of touch-paper will 
be produced. This property is, however, exhibited by the salts of some other 
acids. 

Nitric acid is a substance much used in the laboratory, and in many of the 
operations of practical art. 

341. Protoxyd of Nitrogen, NO \— Nitrous Oxyd ;— Exhilarating 
Gas. — This gas was discovered by Priestley in 1116, but its properties re- 
gained unknown until investigated by Davy, in 1808. Since this period, a 
considerable degree of popular attention has always been bestowed upon it, 

Questions. — Explain the action of nitric acid upon the metals, and the principle which 
6uch action illustrates. What are the salts of nitric acid termed ? What are their dis- 
tinguishing peculiarities? When and hy whom was protoxyd of nitrogen discovered ? 



232 



INORGANIC CHEMISTRY. 



Fig. ill. 



in consequence of the remarkable effects which it produces upon the animal 
system, when taken into the lungs. 

342. Preparation . — Protoxyd of nitrogen is prepared by heating the 
salt known as nitrate of ammonia in a 
glass flask, furnished with a perforated 
cork and a bent glass tube, over a spirit 
lamp* (See Fig. 111.) 

Upon the application of a moderate tem- 
perature, the salt melts, and at about 400° 
F. apparently begins to boil; it is, how- 
ever, in reality undergoing a process of de- 
composition, by which it is entirely re- 
solved into gaseous protoxyd of nitrogen 
and steam (water). The temperature must 
be very carefully watched, and not allowed 
to rise so high as to occasion white vapors 
in the flask, as, in such case, some injurious 
products may be formed. The gas should 
be collected in a gasometer, or receiver rilled with water of a temperature of 
about 90 ; cold water absorbing considerable quantities of it. It is also ad- 
visable to allow the gas to remain for a little time over water before attempt- 
ing to respire it. 

The reaction which takes place in the production of protoxyd of nitrogen 
may be explained as follows : Ammonia is a compound of nitrogen with hy- 
drogen. When the nitrate of ammonia is heated, the hydrogen of the am- 
monia combines with a part of the oxygen of the nitric acid to form water, 
Whilst the nitrogen of the ammonia at the same time becomes oxydized at the 
expense of another part of the oxygen of the nitric acid. The result is, that 
the whole of the nitrogen, both of the nitric acid and of the ammonia, is lib- 
erated in the form of protoxyd of nitrogen, thus : 




ammonia. 



Protox. nitrog. Water. 



NH 3 , NOs, HO becomes 2 NO + 4 HO 

An ounce of nitrate of ammonia will furnish about 500 cubic inches of this 
gas. 

343. Properties . — Protoxyd of nitrogen is a transparent, colorless 
gas, with a sweetish smell and taste. It is a heavy gas, its specific gravity 
being T52, or nearly the same as that of carbonic acid. It supports the com- 
bustion of many bodies with nearly the same energy and brilliancy as pure 



* Nitrate of ammonia is a white crystalline salt, which can be cheaply purchased of 
dealers in chemicals, or can be easily made by neutralizing dilute nitric acid by carbonate 
of ammonia. In preparing exhilarating gas, not less than 6 or 8 ounces should be used. 

Questions. — How is it prepared ? What is the chemical reaction involved in the pro- 
cess ? What are its properties ? 






NITROGEN. 



233 



oxygen ; and when mixed with an equal bulk of hydrogen, forms an explosive 
mixture. It is, however, easily distinguished from oxygen by its ready solu- 
bility in cold water, which dissolves nearly its own volume of the protoxyd 
of nitrogen. 

Under a pressure of 50 atmospheres at 45° F., it is reducible to a clear 
liquid, which, at a temperature of about 150 degrees below zero, freezes into 
a beautiful transparent crystalline solid. By mixing the liquid protoxyd with 
another very volatile substance, the bisulphide of carbon, and allowing the 
mixture to evaporate in vaccuo, M. Natterer, a few years since, obtained a 
reduction of temperature which he estimated at 220 degrees below zero ; — a 
lower point than has been hitherto attained to by any other process. 

Protoxyd of nitrogen, if quite pure, or merely mixed with atmospheric air, 
may be respired for a few minutes without inconvenience or danger. It then 
produces a singular species of transient intoxication, " attended in many in- 
stances with an irresistible propensity to muscular exertion, and often to un- 
controllable laughter ; hence the gas has acquired the popular name of exhil- 
arating or laughing-gas. Different individuals are affected in different degrees 
and in various ways, according to the temperament of each. In plethoric 
persons, where there is any tendency to over-active circulation through the 
brain, the experiment is not a safe one. The intoxicating effects pass off in 
a few minutes, and frequently no recollection of what has passed is retained, 
and no lassitude is perceived after the extreme exertion." — Miller. The gas 
should be inhaled from a large bladder or gas-bag, through a tube of an inch 
internal diameter. 

An animal entirely immersed in this gas soon dies from the prolonged ef- 
fects of the intoxication. 

The idea that ansesthesis, or insensibility to pain during surgical operations, 
might be occasioned by the inhalation of gases, appears to have been first en- 
tertained by Dr. Horace Wells, of Hartford, Conn., from observing the action 
of protoxyd of nitrogen upon the animal system ; and he succeeded in pro- 
ducing, by means of it, the same effects which are now accom- 
plished by the agency of chloroform and ether. / 
344. Deutoxyd of Nitrogen, N0 2 : Binoxyd of M~ 
. Irogen, or Nitric Oxyd. — This gas is easily prepared by pouring 
nitric acid upon clippings or turnings of copper, contained in 
a flask with a little water. As no heat is required, the double- 
tubed hydrogen gas apparatus may be employed. (See Fig. 
112.) At the commencement of the action, the flask becomes 
filled with deep-red fumes, but if the gas be collected over 
water it will be found to be colorless. 

The chemical action involved in tho production of nitric- 
oxyd, by this process, is as follows : The copper takes oxygen from one por- 

Qtjestions. — How is it distinguished from oxygen ? What effect has cold or pressure 
upon it ? "What effect does protoxyd of nitrogen produce upon the system when inhaled ? 
What discovery -was first suggested by the action of this gas on the system ? How is 
nitric oxyd prepared ? What is the chemical action involved ? 



Fig. 112. 




234 INORGANIC CHEMISTRY. 

tion of the nitric acid and becomes oxyd of copper, which combines with an- 
other portion of acid remaining undecomposed, and forms the nitrate of cop- 
per, the solution of which is of a blue color. That part of the nitric acid which 
is decomposed, loses three equivalents of oxygen, which are taken up by the 
copper ; the remaining two equivalents of oxygen united with the nitrogen 
appear as the gas, thus : 

Copper. Nitric acid. Nitrate copper. Nitric oxyd. 



3Cu.-f-4(N0 5 ) = 3 (Cu.O, N0 5 ) + N0 2 

345. Properties , — Nitric oxyd is a colorless gas, which is but slightly 
absorbed by water. It is perfectly irrespirable, and excites a violent spasm 
of the throat when an attempt is made to respire it. Sir Humphrey Davy, in 
his experiments upon the respiration of the protoxyd of nitrogen, attempted 
to inhale this gas, but the result was nearly fatal, and would have been quite 
so, had not the glottis contracted spasmodically, and thus prevented its pas- 
sage into the lungs. 

Most burning bodies, when immersed in this gas, are extinguished by it, 
although it contains half its weight of oxygen. If phosphorus and charcoal, 
however, in a state of ignition, be introduced into it, the heat they evolve 
effects the decomposition of the gas, and the combustion continues with great 
brilliancy through the agency of the liberated oxygen. 

The most remarkable property of nitric oxyd appears to be its great attrac- 
tion for oxygen. "When mixed with oxygen, or any gas containing oxygen 
(atmospheric air), dense red fumes are produced, which are soluble in water, 
and produce an acid liquid. In this way nitric oxyd may be used as a test 
to demonstrate the presence of uncombined oxygen in a gaseous mixture. 
Experimentally this action may be demonstrated as follows : Partially fill a 
tall glass jar or bottle with nitric oxyd, over a pneumatic trough ; and then 
by lifting the end of the jar, admit a few bubbles of atmospheric air, or pure 
oxygen. In an instant, deep blood-red fumes will fill the vessel, and much 
heat will be generated. By agitating the contents of the jar with water, the 
red vapors are rapidly absorbed, and the experiment may be several times 
repeated, with the remaining portions of the gas. 

Nitric-oxyd has never been liquefied. 

346. Nitrous Acid, IV 3 . Byponitrous Acid. — The third compound 
of nitrogen with oxygen is a brownish red vapor at ordinary temperatures, 
and a volatile green liquid at a temperature 0° F. It is formed by mixing 
4 volumes of nitrous oxyd with 1 volume of oxygen, both in a perfectly dry 
state. It unites with bases to form salts, which are called nitrites. 

347. Hyponitric Acid, N 4 . Peroxyd of Nitrogen. — The red fumes 
which appear in mixing nitrous oxyd with oxygen, or atmospheric air, con- 

Qtjestions. — What are its properties ? How does it act upon combustibles ? "What is 
the most remarkable characteristic of nitric oxyd ? How may it be illustrated ? What 
is the physical condition of nitrous acid ? How is it prepared ? What is said of hyponi- 
tric acid ? 



CHLORINE. 



235 



sist mainly of hyponitric acid. It may be formed in a state of purity, by 
mixing 4 volumes of Nitric-oxyd with 2 volumes of oxygen. 

The compounds of nitrogen with hydrogen, carbon, and other non-metallic 
elements, will be considered in subsequent sections. 

SECTION Y. 






CHLORINE. 

Equivalent, 35*5. Symbol, Cl. Density, 2*47. 

348. History .—This substance was discovered by Scheele 
in 1774, and called by him dejihlogisticated marine acid. 

It was universally regarded as a compound body until 1811, when Davy 
established its elementary character, and on account of its yellowish-green 
tint, gave it the appellation of chlorine (from ^Aw/iof, green). 

349. Natural History and Distribution. — Chlorine is a 
principal member of a small natural group of four closely-allied elementary 
bodies, viz., chlorine, iodine, bromine, and fluorine, which differ in many re- 
spects from all the other elements. They are characterized by a remarkable 
indifference for each other, and for an intense affinity for other substances at 
ordinary temperatures — an affinity so general as to preclude the possibility of 
any member of the class existing in a free and uncombined state in nature. 



Fia. 113. 



Collectively they are termed the Halogens, from the 
circumstance of their forming with the metals saline 
compounds resembling common salt. — Haloid salts. 
/See §271.) 
i Chlorine united with other elements is a large con- 
/ stituent both of the inorganic and organic kingdoms. 
/ The great magazine of it in nature is rock, or common 
V salt, which is a compound of chlorine and the metal 
X^sodium. Combinations of it also with other substances 
in the mineral kingdom are not unfrequent. In the or- 
ganic kingdom it is found as a constituent of both an- 
imals and vegetables ; existing in the greater number 
of animal liquids, and in various fluids and secretions 
of plants. 

350. Preparatio n. — Chlorine is most easily pre- 
pared by pouring strong hydrochloric (muriatic) acid 
upon pulverized binoxyd of manganese contained in a 
glass retort or flask (arranged as in Fig. 113), and ap- 
plying a gentle heat from a spirit-lamp. The propor- 
tions winch give the best result are, one part by weight 



Questions. — How is it prepared ? Give the history of chlorine. To what other ele- 
ments is chlorine allied? What are the characteristics of these associated elements? 
What designation is given to them as a class ? What is said of the distribution of chlor- 
ine in nature ? How is it prepared ? 




236 INORGANIC CHEMISTRY. 

of binoxyd of manganese, and two parts by weight of hydrochloric acid. The 
gas may be collected over water, or more conveniently by the displacement 
of air in a dry, narrow-necked jar, as is represented in Fig. 113. The green- 
ish color of the chlorine enables the operator to determine when the receiver 
is full. By closing the jars with glass stoppers, well smeared with tallow, the 
gas can be preserved unaltered for a considerable length of time.* 

The chemical reaction which takes place in this process may be explained 
as follows : hydrochloric acid is a compound of hydrogen and chlorine ; when 
mixed with the binoxyd of manganese in the proportion of 2 equivalents of 
the former to 1 of the latter, double decomposition ensues: — water, free 
chlorine, and a chloride of the metal being produced. 

Thus,— Mn0 2 -f-2HCl=MnCH-2HO-hCl. 

Three ounces of powdered binoxyd of manganese with half a pint of com- 
mercial muriatic acid diluted with 3 ounces of water, will yield between three 
and four gallons of the gas. Care should be taken not to use an acid more 
dilute than the one indicated, lest some explosive compound of chlorine should 
be generated. 

Chlorine may also be readily obtained by distilling a mixture of 4 parts by 
weight of common salt, 1 part of binoxyd of manganese, 2 of sulphuric acid, 
and 2 of water. It is in this way that chlorine is prepared in enormous quan- 
tities for manufacturing purposes ; but for the preparation of " chloride of 
lime," the first described method is followed, owing to the fact that the hy- 



* The following memoranda respecting the preparation of chlorine are -worthy of atten- 
tion. The process should always he conducted in a well-ventilated apartment, altogether 
free from valuable furniture, and especially from colored curtains, paper-hangings, etc. — 
the action of the gas being most destructive of the color and texture of organic compounds. 

Before applying heat to the generating flask, the operator should observe whether the 
interior of the glass has become thoroughly wetted by the acid, or whether a dry spot 
still remains. If the latter is the case, all heat should be withheld until the mass by agi- 
tation has become thoroughly incorporated, and the dry spot disappears. If this precau- 
tion is neglected, a fracture of the retort will probably take place on the application of 
heat. Most authorities recommend the collection of chlorine over warm water, inasmuch 
as cold water absorbs a considerable amount of the gas. This plan is attended with the 
serious disadvantage of causing chlorine to enter the bottle hot, and for that reason rare- 
fied ; so that when it cools and contracts, the stoppers of the bottles are found not unfre- 
quently to be permanently fixed. Cold water should be employed, and except it be agi- 
tated whilst the gas is passing through it, bo little of the chlorine is absorbed that the 
amount of loss is too small to be of consequence. — Faraday. 

Every care should be taken in bottling up chlorine for preservation, to exclude water ao 
much as possible, inasmuch as under the agency of light, water and chlorine react, form- 
ing hydrochloric acid, which is so violently absorbed by water, that the stoppers of the 
chlorine bottle3 become often irremediably fixed, owing to external pressure. — Ibid. 

If the operator during the preparation of chlorine should • inadvertently inhale a dis- 
agreeable quantity of the gas, the most effectual relief will be obtained from an immediate 
application of ammonia (smelling-salts) to the nostrils, or from inhaling the vapor of al- 
cohol or ether. 

Questions.— What precautions are to be observed in its preparation? "What is the 
chemical action involved in this process ? By what other process may chlorine be pre- 
pared ? For what practical purposes are these two processes applied ? 



CHLORINE. 237 

drochloric acid used is obtained as a waste product in the manufacture of 
carbonate of soda (soda-ash) from sea-salt. 

351. Properties . — Chlorine is a dense, heavy gas, of a greenish-yel- 
low color. It is characterized by a peculiar suffocating odor, almost intoler- 
able to most persons even when greatly diluted with air, and occasioning a 
distressing irritation of the air-passages of the throat, attended with cough- 
ing. Any attempt to respire the gas in a pure form would probably be fatal, 
but wheu largely diluted with air, it is breathed without inconvenience by 
workmen in manufacturing establishments, and it has also been adopted a3 
a remedial agent in this condition with benefit for pulmonary diseases. It 
should not, however, be used for this latter purpose without the sanction of 
a medical authority. 

Chlorine is one of the heaviest of the gases, its specific gravity being 2*47 
(air =» 1). Under a pressure of 4 atmospheres, at 60° R, it condenses to a 
yellow liquid, of specific gravity 1*33, which remains unfrozen even at a cold 
of— 220° F. 

Cold water absorbs about twice its bulk of chlorine gas. This solution, 
which is readily formed by agitating the gas and the water together, ac- 
quires the color, odor, and other properties of chlorine, and is much used for 
experimental and manufacturing purposes in preference to the pure gas. As 
it is slowly decomposed by the action of light, it should be preserved in 
bottles covered with paper, or in a dark place. 

"With water near its freezing point chlorine combines to form a definite 
hydrate, which contains 10 equivalents of water (Cl-f-10HO) ; this at a tem- 
perature of 32° F. freezes and forms beautiful yellow 
crystals. If these crystals be hermetically enclosed FiG. 114. 

in a glass tube (see Fig. 114), they will, when ex- 
posed to a gentle heat, liberate free chlorine ; this 
prevented from expanding, presses upon itself to 
such an extent that a portion of the gas liquefies, 

and may then be seen in the tube, floating upon the water which is 
present. This process furnishes the most ready way of obtaining liquid 
chlorine. \ 

352. Chlorine is a supporter of combustion, but its effects are strikingly 
different from those manifested by oxygen. It does not combine directly wit 1 ' 
either oxygen or carbon, but has a most powerful affinity for hydrogen anu r 
the metals. Therefore, bodies rich in oxygen and carbon, either burn indif- 
ferently in chlorine or not at all, as in the case of charcoal ; but on the con- 
trary, bodies rich in hydrogen, together with many of the metals, burn in it 
with great brilliancy. The following experiments are illustrative of these 
facts : 



Questions. — What are the general properties of chlorine ? Is it at all respirahle ? 
What is the density of chlorine? Can it be liquefied ? What is a solution of chlorine ? 
What are its properties ? What combination does chlorine form with water ? How may 
liquid chlorine be prepared ? What are the relations of chlorine to combustion ? 



238 



INORGANIC CHEMISTRY. 



A piece of flaming charcoal plunged into a vessel of chlorine is extinguished 
as instantly and as completely as if plunged into a vessel of water. ' 

"Wax and tallow are compounds of carbon and hydrogen. If a lighted 
taper be immersed in a jar of chlorine, its flame is extinguished ; but the 
column of oily vapor rising from the wick is rekindled by the chlorine ; tho 
hydrogen part of the combustible burning with a dull reddish flame, while 
the carbon is separated in the form of a dense black smoke. 

Another experiment illustrates the same action in a more remarkable man- 



Fig. 115. 




ner. Oil of turpentine is a liquid exceedingly rich in hy- 
drogen, and also in carbon. If a piece of paper soaked in 
it be fastened to the end of a rod and plunged into a jar of 
chlorine (see Fig 115), the chlorine unites with the hj-dro- 
gen so readily as to instantly produce spontaneous combus- 
tion, while the carbon is separated and deposited as an 
abundant soot. 

If a bit of ignited phosphorus be immersed in a jar of 
chlorine, as is represented in Fig. 116, the combustion con- 
tinues, but the light evolved is hardly perceptible. If a 
piece of phosphorus be plunged into chlorine without ig- 
nition, it inflames spontaneously — a result which does not 
take place in oxygen. The feeble light which accompanies 
the combustion of phosphorus in chlorine, therefore, can not 
be explained by reason of any lack of affinity 
between these two substances, but it is due to 
the fact that the immediate products of the com- 
bustion are vaporous or gaseous, and are not 
rendered luminous by heating. (See Combustion.) 
Antimony and many other metals finely pow- 
dered, and projected into a vessel of chlorine, take 
fire and produce a brilliant combustion. Thin 
sheets of copper leaf, attached to a copper wire, 
and dipped into chlorine, exhibit the same phe- 
nomenon. 

<-» 353. The intense affinity which chlorine mani- •§ 
fests for hydrogen is one of the most remarkable 
characteristics of this element, and is the property, above all others, which 
gives to chlorine its great value as an industrial agent. This affinity is, how- 
ever, regulated, or rather called forth, by a most singular action of light. 
Thus, when chlorine and hydrogen, in the gaseous condition, are mixed to- 
gether in equal volumes, they will remain for an indefinite period without 
action upon each other, if kept in the dark. If the mixture be exposed to 
diffused daylight, combination will take place gradually ; but if the two gase3 




Questions. — What experiments illustrate its action in this respect ? "Why does phos- 
phorus hum in chlorine with a feehle light ? What are the relations of chlorine to hy« 
drogen ? What influence does light exert upon a mixture of these two elements ? 



CHLORINE. 239 

are brought into direct sunlight, the union takes place instantly, accompanied 
with a powerful explosion.* 

The following experiment is illustrative : Select a clear glass bottle (holding 
about a pint), and fill it over a pneumatic trough, to the extent of half its 
capacity, with chlorine gas ; then carefully cover the bottle with a dark cloth, 
and add hydrogen from a gasometer sufficient to occupy the remaining space, 
or until all the water in the bottle is displaced ; cork the bottle, keeping its 
mouth under water, and remove it from the trough carefully and entirely en- 
veloped in the cloth. Then place the bottle in the direct light of the sun, and 
from a distance remove the cloth by means of a string or a long pole. If the 
preliminary conditions have been strictly complied with, the instant the rays 
of light fall upon the mixture a violent explosion will occur. 

When chlorine in a free state, or in feeble combination with some other 
substance, is brought in contact with a body which contains hydrogen as one 
of its constituent elements, it manifests the same affinity for this element ; and 
tends to " draw out," as it were, the hydrogen from its combination, and by 
uniting with it, to change or destroy the original compound. In this instance, 
also, light exercises a controlling influence. 

For example: If a solution of chlorine in water (§ 351) be kept in the 
dark, no change takes place in it ; but when exposed to the action of sun- 
light, it decomposes readily. This result is produced by the following reac- 
tion : — the chlorine contained in the solution, by reason of its intense affinity 
for hydrogen, withdraws this element from its combination with oxygen in 
the water, and uniting with it, forms an acid ; the oxygen of the decomposed 
water, being no longer held in combination, escapes as a gas. , . 

354. T h e o r y of B 1 e a c h i n g — It is this action of chlorine upon hy- 
drogen which renders chlorine the most powerful of all known bleaching and 
deodorizing agents. Nearly all animal and vegetable coloring matters contain 
hydrogen as one of their essential constituents. "When brought in contact 
with chlorine, the hydrogen they contain unites with it, and the original ar- 
rangement of particles, upon which the color of the body depended, being 
thus changed or broken up, the color itself is destroyed. Ozone, which is also 
a powerful bleaching agent, acts in a similar manner ; the oxygen of which 
it consists, by reason of its highly active condition, withdraws hydrogen from 
its combination, unites with it to form water, and thus destroys the arrange- 
ment upon which the color depends. By withdrawing a single pillar of sup- 



* It has also been shown by Dr. Draper, that pure and dry chlorine gas, when exposed 
for a time to the action of the sun's light, acquires and retains, for a considerable period, 
the power of forming an explosive union with hydrogen, even in the dark ; while, on the 
other hand, chlorine prepared in the dark manifests no affinity for hydrogen until exposed 
to the light. This peculiar action of light is entirely confined to the chemical element of 
the solar ray. 

Questions What experiment illustrates this? What are the relations which chlorine 

sustains to hydrogen in combination ? Illustrate by example. What is the theory of bleach- 
ing by chlorine ? By ozone ? What is said of the permanency of the bleaching effect of 
of these agents ? 



240 INORGANIC CHEMISTRY. 

port, the whole structure falls. Colors once removed by the action of chlorine 
or ozone can never be restored ; and in this respect these two substances dif- 
fer from most other bleaching agents. 

The bleaching action of chlorine may be illustrated by a variety of experi- 
ments. For this purpose a solution of chlorine in water may be most con- 
veniently used. If we pour a little of this solution upon red ink, red wine, 
the blue tincture of red cabbage, of litmus, on indigo solution, or on ordinary 
writing ink, their several colors almost immediately disappear. Paper, col- 
ored rags, and all varieties of cotton or linen fabrics immersed in a solution of 
chlorine, are bleached with great rapidity. The moist gas produces the same 
effect, but perfectly dry chlorine will not bleach. Fibres of wool are not 
bleached by the action of chlorine, neither is it usually employed for the 
bleaching of silk. It has no action upon "India," or printers' inks, for the 
reason that the coloring matter in these cases consists of minutely-divided 
carbon, which does not combine directly with chlorine.* By contact with 
chlorine for any considerable length of time, the texture of almost all organic 
substances is weakened and destroyed. This may be especially noticed in 
cases where cotton or linen fabrics have been wet with a chlorine solution, 
and then allowed to dry, without previous thorough washing. 

355. Disinfecting and Deodorizing Action of Chlorine. 
— Chlorine acts upon noxious and odorous vapors and organic compounds to 
decompose and destroy them, in the same way as it does upon coloring agents. 
It differs essentially in its action from many substances used in fumigation, 
such as burnt paper, vinegar, pastiles, perfumes, and the like, inasmuch as, 
while the latter only disguise the ill odors, or mephitic atmosphere, by substi- 
tuting one smell for another, the chlorine absolutely destroys the noxious 
matter itself. 

The use of chlorine as a disinfectant, however, requires care. It should be 
used in the form of bleaching-powder (" chloride of lime"), mixed with water, 
and exposed to the air, in shallow vessels, if possible upon a high shelf. This 
compound is gradually decomposed by the carbonic acid of the atmosphere, 
and the chlorine being evolved falls slowly down, and is diffused through the 



* A very elegant application of chlorine to bleaching purposes is made in the printing 
of bandanna handkerchiefs. The -white spots, -which constitute their peculiarity, are 
thus produced ; First of all, the whole fabric is dyed of one uniform tint, and dried. 
Afterward many layers of these handkerchiefs are pressed together between lead plates, 
perforated with holes conformable to the pattern -which is desired to appear. Chlorine 
solution is now poured upon the upper plate, and finds access to the interior through the 
perforations. By reason of the great pressure upon the mass, the solution can not, how-' 
ever, extend laterally further than the limits of the apertures, whence it follows that the 
bleaching agent is localized to the desired extent, and figures corresponding in shape and 
size to the perforations are bleached white upon a dark ground. — Faeatjay. 

Questions. — How may the bleaching action of chlorine be illustrated ? What are ex- 
ceptions to its action? What effect does continued contact with chlorine have upon 
organic substances? What is the disinfecting and deodorizing action of chlorine ? How 
does chlorine differ in its action from many fumigating agents ? How should chlorine be 
applied for disinfection and deodorizing ? 



CHLORINE. 241 

room. If a more rapid action is required, a little dilute sulphuric or hydro- 
chloric acid may be allowed to drop into the chloride of lime solution from a 
vessel suspended above it, by means of a piece of lamp-wick arranged in the 
form of a syphon. Another method is to suspend in the apartment, cloths 
steeped in a solution of bleaching-po wder ; and in the absence of bleaching- 
powder, the gas may be easily generated by one of the methods already de- 
described — care being taken to avoid excess.* 

356. Compounds of Chlorin c. — Chlorine combines with all the 
non-metallic elements, with perhaps a single exception. With many of them, 
however, it can not be made to unite directly. It enters into combination 
with all the metals ; and with a large number of them directly, with an evo- 
lution of light and heat. The binary compounds of chlorine are termed » 
chlorides. With the exception of the chlorides of sdver and lead, and the sub- 
chlorides of copper and mercury, they are all more or less soluble in water, 
and in their taste and general physical character, resemble common salt. 

It frequently happens that chlorine combines with the same metal in moro 
proportions than one : for example, with iron, a protochlorido (Fe CI) and a 
sesquichloride (Fe 2 Cl3) may be formed; and with platinum a protochlorido 
(Pt CI) and a bichloride (Pt Ch) ; and, generally, for each oxyd of the metal 
that is capable of uniting with acids to form salts, a corresponding chloride 
exists. 

Most of the chlorides of the metals are solid ; but some few are liquid at 
ordinary temperatures ; and one, the perchloride of manganese (Mm CI?) is 
gaseous. All of them are fusible at a moderate temperature, and many , 
are readily volatilized in the operation ; especially is this true of the chlor- 
ides of gold, copper, aluminum, magnesium, and several others. Geol- 
ogists have taken advantage of this fact, in some instances, to explain the 
formation of mineral, or metallic veins in the rocky strata composing the crust 



* " It must be particularly borne in mind, that chlorine in any form must only be used 
as an aid to proper ventilation. It is a necessary condition of health that our houses and 
rooms be properly ventilated. There is no substitute for ventilation any more than for 
■washing or for general cleanliness. Chlorine, like medicine, ought in general to be used 
on special occasions, and under advice. In a sick-room, where ventilation is often diffi- 
cult, chlorine, liberated in very minute quantities, will often be found singularly refresh- 
ing ; but in this, as in all other cases of fumigation with chlorine, all metallic articles in 
the apartment ought to be removed, for these become speedily tarnished by the action of 
chlorine. 

" For disinfecting the wards of hospitals and similar places, Prof. Faraday found that 
a mixture of 1 part of common salt, and 1 part of the binoxyd of manganese, when acted 
upon by 2 parts of oil of vitriol previously mixed with 1 part of water (all by weight), and 
left till cold, produced the best results. Such a mixture at 60° F., in shallow pans of 
earthen ware, liberated its chlorine gradually but perfectly in four days. The salt and 
the manganese were well mixed and used in charges of 3^ pounds of the mixture. The 
acid and water were mixed in a wooden tub, the water being put in first, and then about 
half the acid ; after cooling the other half was added: The proportions of water and acid 
are 9 measures of the former to 10 of the latter." 

Questions. — "What is said of the compounds of chlorine ? What are the compounds 
of chlorine termed ? What are the general properties of the chlorides ? 

11 



242 



INOKGANIC CHEMISTRY. 



\ 



of our globe. It is supposed that the metals, in the form of chlorides, have 
been sublimed or volatilized by intense heat from the interior of the earth, and 
rising through openings and fissures in the rocks, have been deposited, as they 
cooled, in the situations in which they are now found. 

Formerly, before the constitution of chlorine was fully understood, its com- 
pounds with the metals were termed muriates. The names, muriate of tin, 
muriate of soda, muriate of iron, have therefore the same signification as 
chloride of tin, chloride of soda, chloride of iron, etc. 

357. Hydrochloric Acid, H C 1 — Chloroliydric Acid ; 
Chloride of Hydrogen; Muriatic Acid. — This substance, 
formed by the union of chlorine and hydrogen, is the most 
important of all the compounds which chlorine forms with 
the non-metallic elements. 

It was first obtained by Priestley in its pure form of a gas, in 1112 ; and in 
a state of solution in water, it has long been known under the names of muri- 
atic acid, and spirit of salt. In the latter condition it constitutes a strong, 
corrosive acid liquid. 

358. Preparatio n, — When chlorine and hydrogen are mixed together 
in the proportion of equal volumes, and a chemical combination is effected 
between them, they unite, without condensation, to form hydrochloric acid 
gas. This union may be brought about by the action of light, in the manner 
before described (§ 353), by the application of an ignited match, or by the 
passage of the electric spark — the combination in the latter instances being 
always attended with an explosion. 

For experimental purposes, hydrochloric 
acid gas may be procured by heating in a 
glass flask, furnished with a perforated cork 
and tube, a quantity of strong commercial 
muriatic acid. The gas is readily given off 
by the application of a gentle heat, and may 
be collected by displacement of air in dry 
vessels. (See Fig. 117.) 

For most practical purposes, hydrochloric 
acid is obtained by action of sulphuric acid 
upon common salt. When the process is 
conducted on a small scale, and in a glass retort, or an apparatus similar to 
that represented in Fig. 117, 3 parts of common salt, 5 of strong sulphuric 
\ acid, and 5 of water may be taken. The reaction in this ease is as follows : 
\ common salt is composed of chlorine and sodium ; when mixed with sulphuric 
acid and water, the water is decomposed ; its hydrogen uniting with the 
chlorine of the common salt to form hydrochloric acid, and its oxygen with 



Fig. 117. 




Questions. — What theory has been proposed to account for the origin of mineral veins? 
What are muriates ? What is hydrochloric acid ? How may it be prepared ? How is it 
prepared for practical purposes? 



CHLORINE. 243 

the sodium to form soda, which last unites with the sulphuric acid to form 
sulphate of soda. Expressed in symbols, we have — 



Common salt. Sulph. acid. Water. Sulphate of soda. Hydrochloric acid. 

NaCl 



-j- S0 3 + HO — NaO,S0 3 -j- HC1 

359. Properties . — Hydrochloric acid is a colorless acid gas, of a pe- 
culiar pungent odor, producing white fumes when allowed to escape, by 
uniting with and condensing the moisture of the atmosphere. It is quite un- / 
rc-spirable, but is much less nauseous and suffocating than chlorine. It pro- 
educes coughing when breathed in even the most dilute condition. It is heavier 
than air, and has a specific gravity of T24. Under a pressure of 40 atmos- 
pheres at 50° F., it condenses to a colorless liquid, which has never been 
frozen. It is incombustible, extinguishes burning bodies and when brought 
in contact with dry and blue litmus paper reddens it. 

Hydrochloric acid gas is especially characterized by a most intense attrac- 
tion for water, which liquid at a temperature of 40° F. is capable of absorbing 
about 480 times its bulk of gas — increasing in volume thereby about one 
third, and acquiring a specific gravity of 1*21. Water of a higher temperature 
absorbs less. A piece of ice passed into a jar of hydrochloric acid gas stand- 
ing over mercury is instantly liquefied by it ; and the gas at the same mo- 
ment disappearing by absorption, the mercury rises to fill the jar. By reason 
of its great solubility in water, it can only be collected over mercury, or by 
the displacement of air. / — 

360. Solution of Hydrochloric Acid, which constitutes 
the liquid acid, or the muriatic acid of commerce, is pre- 
pared by generating the gas from a mixture of salt and 
dilute sulphuric acid, and allowing it to pass through and 
become absorbed by water. 

The gas is conducted from the retort or generating vessel into a series of 
bottles or jars connected with each other and filled with water: When the 
water in the first vessel becomes saturated with hydrochloric acid, the gas 
passes over into the second, thence into the third, and so on, saturating each 
successively. Several contingencies, however, must be provided for in this 
operation ; the evolution of gas may take place so rapidly as to rupture the 
receivers, or the gas delivered slowly may be absorbed so completely by the 
water as to produce a vacuum ; in which case the whole liquid contents of 
the receivers flow back violently into the retort, and thus put an end to the 
process. X 



Questions. — Explain the chemical reaction in this case ? What are the properties of 
hydrochloric acid gas ? What is said of its attraction for water ? What is the muriatic 
acid of commerce ? How is it prepared ? What precautions are to be observed in its pre- 
paration ? 



244 



INORGANIC CHEMISTRY, 



Woulfe's Apparatus .-—To obviate these difficulties, a series of 
peculiar- shaped vessels, known as "Woulfe's bottles," are employed. These 
consist of glass jars, or bottles, provided with three necks, or apertures, (see 
Fig. 118), each of which is fitted with a perforated cork and tube. The man- 
ner in which the gas enters and is discharged from the vessel will be readily 
understood by an inspection of the figure. The middle aperture is fitted with 
a sm^le upright tube, called the " safety tube," which dips beneath the sur- 
face* af the liquid contained in the vessel. If the pressure of gas becomes 

Fig. 118. 




excessive, the water is forced up the center tube, and the pressure is relieved. 
If a vacuum is created, air enters from without to fill it. By the condensa- 
tion of the hydrochloric acid gas, much latent heat is liberated, and the water 
which absorbs it soon becomes elevated in temperature ; to obtain, therefore, 
the most concentrated solution of gas, it is necessary that the receivers should 
be immersed in cold water, or surrounded with ice. Connection between the 
separate Woulfe's bottles is effected by means of a flexible tube of India- 
rubber. 

Hydrochloric acid solution, when pure, is a colorless liquid, fuming, when 
concentrated, on exposure to air. The commercial " muriatic" acid is gener- 
ally of yellow, or straw color, owing to the presence of iron and other impu- 
rities. It constitutes one of the three great acids of commerce, and is exten- 
sively used as a reagent in chemical operations, and to some extent in medi- 
cine as a tonic. In the manufacture of " soda ash" (carbonate of soda), by 
the decomposition of common salt, hydrochloric acid gas is prepared as an 
incidental product in immense quantities ; and in some of the great manu- 
facturing establishments of Great Britain it is regarded as a waste product, 
the disposal of which is attended with difficulty and expense.* 



* It was usual to allow the acid gas to escape into the air by means of a chimney, on 
emerging from the top of which it formed, in contact with moisture, white clouds of acid, 



Questions. — Describe the construction and use of Woulfe's bottles. What are the 
physical properties of hydrochloric acid solution? What are its uses? Of what branch 
of manufacture is it an incidental product ? 



CHLORINE. 245 

Free hydrochloric acid, derived from the salt contained in food, is found in 
the stomach, as a constituent of the gastric juice. Its presence, and that of 
the soluble chlorides in solution, is indicated by the formation of a white, 
curdy precipitate, when nitrate of silver in solution is added to the liquid. 
This precipitate — chloride of silver — is soluble in ammonia, but insoluble in 
nitric acid. 

361. Aqua Regia. — Nitro-Muriatic Acid. — The name of 
aqua regia {royal water) was given by the alchemists to a 
mixture of nitric with, hydrochloric acid, from the power 
that it possesses of dissolving gold, the " king of the 
metals/' 

Gold and platinum are insoluble in either acid separately ; but when the 
two acids are mixed, they mutually decompose each other in the presence of 
the metals — free chlorine, and a compound of chlorine and an oxyd of nitrogen 
being liberated. The chlorine, in the moment of its extrication, or in its 
nascent state (page 162), acts upon the metals and dissolves them — the pro- 
ducts formed being chlorides. 

The best proportions of aqua regia are one of nitric acid by measure to two 
hydrochloric. 

362. Ox yds of Chlorine . — Although chlorine and oxygen will not, 
under any circumstances, unite directly, several compounds of these elements 
may be obtained by indirect methods. The composition and names of the 
most important are indicated in the following table : — 

Composition by weight. 

Symbol. , ■ ■> 

Hypochlorous acid CIO 35*5 chlorine. 8 oxygen. 

Chlorous acid C103 35-5 « 24 « 

Peroxyd of chlorine C104 35*5 " 32 " 

Chloric acid CIO5 35-5 " 40 " 

Hyperchloric acid CIO7 35*5 " 56 " 

363. Hypochlorous Acid . — This compound may be produced by 
the action of chlorine upon red oxyd of mercury. It is a yellow gas, readily 



■which, -wafted by the wind, produce a corrosive rain, most ruinous to the vegetation of 
the surrounding country. Many soda works in Great Britain were, therefore, indicted aa 
nuisances on this account, and attempts were made to remedy the evil by discharging the 
fumes at great elevations, where it was supposed they would become so diluted by admix- 
ture with vapor as to be rendered harmless. To carry out this scheme, the most giganti« 
chimneys ever built were constructed. One near Liverpool is 495 feet high, 30 feet in 
diameter at the base, 11 feet at the top, and contains a million of bricks. Another at 
Glasgow is still larger. These costly structures have not, however, been found to answer 
the purpose for which they were intended, and it has become necessary to condense the 
gas as fast as it is liberated by bringing it into contact with cold water. But even this, 
taken in connection with the disposal of the great quantity of liquid acid formed, is a 
matter of great difficulty, and many arrangements have been patented to effect it. 

Qttestions. — Does it exist in the animal economy ? What is a test of its presence ? 
What is aqua regia ? Why so called ? How is it enabled to dissolve gold ? What is said 
of the oxyds of chlorine ? What is hypochlorous acid ? 



246 INORGANIC CHEMISTRY. 

absorbed by water, and condensed by the application of cold into an orange- 
yellow liquid. 

364. Bleaching Compounds. — When chlorine gas is caused to 
pass through weak solutions of the alkalies, or over hydrate of lime (slacked 
lime), it is absorbed, and very peculiar compounds, possessed of remarkable 
bleaching properties, are produced. It is in this way that the bleaching 
agents so extensively used in the arts under the names of chloride of lime 
(bleaching powder) chloride of soda, and chloride of potash, together with 
What are called. " disinfecting fluids," are prepared. 

These compounds, according to the opinion of most chemists, are formed 
by the union of hypochlorous acid with an oxyd of a metal, and are termed 
hypochlorites. Thus the constitution of the so-called chloride of lime would 
be represented in symbols as follows : CaO, CIO. Other authorities deny the 
formation of hypochlorous acid, and regard the compounds in question as 
formed by the direct union of chlorine with an oxyd. According to this latter 
view, the constitution of chloride of lime, represented in symbols, would be as 
follows: CaO, CI. 

365. Chloride of Lime, or Bleaching- Powder, is the most important 
of all the bleaching compounds of chlorine, and is used in immense quantities 
for the bleaching of paper, cotton, and linen fabrics, and for disinfecting pur- 
poses. Its manufacture is almost a monopoly with Great Britain, and no at- 
tempt to prepare it on a large scale in this country has ever proved success- 
ful.* The process consists essentially in exposing fresh slacked lime, spread 
out upon shelves in large leaden or stone chambers, to the action of gaseous 
chlorine — the operation being continued until the lime has absorbed, or united 
with the largest possible amount of the gas. It is then withdrawn, and made 
ready for transportation by enclosure in tight casks. As thus prepared, it is 
a soft white powder, partially soluble in water, and possessing a chlorine-like 
odor. "When exposed to the air it is readily decomposed, carbonic acid being 
absorbed, and chlorine liberated. 

Ordinary bleaching-powders contain about 30 per cent, of available chlo- 
rine. The testing of their commercial value is termed chlorimetry, and the 
method adopted generally consists in ascertaining by experiment how many 
grains of a particular sample are required to destroy the color of a known 
weight of indigo in solution. The result, compared with the results of certain 
standard experiments, gives the percentage. 



* The reason why the manufacture of bleaching-powder has not been introduced into 
the United States, is due doubtless to the fact, that it can only be economically conducted 
in connection with the manufacture of soda-ash, which process furnishes hydrochl ric 
acid, from whence chlorine is procured, at a mere nominal cost ; and to carry on both 
operations advantageously requires the employment of great capital and skill. 



Questions. — How are the ordinary bleaching compounds and "disinfecting fluids" 
formed ? What is said of the composition of these compounds ? What is said of chloride 
of lime ? How is it prepared ? What is chlorimetry ? How is it conducted ? 



CHLORINE. 247 

"What is called " Labarraque's disinfecting liquid," is a solution of a com- 
pound of chlorine and soda., similar in composition to bleaching-powder. 
" Burnet's disinfecting fluid" is a compound of chlorine and zinc. 

366. Chloric Acid, C10 5 . — This compound is not known in an iso- 
lated state, and is never obtained except in combination with water (CIO 5 
IIO). "When a stream of chlorine gas is transmitted through a strong solu- 
tion of caustic potash, the gas is absorbed, and a bleaching solution, as before 
described, is formed. This, by standing, or by the application of heat, loses 
its bleaching property, and becomes a mixture of chloride of potassium and 
chlorate of potash ; the latter of which, being the least soluble, separates on 
concentrating the liquid, into shining tabular crystals. In this reaction, a part 
of the potash is decomposed ; its oxygen combining with one portion of chlor- 
ine to form chloric acid, while the potassium is taken up by a second portion 
of the same substance; or in symbols: — 

6 Cl+6 KO=KO,C10 5 +5 KCI. 

Chlorates of other bases are formed in a similar manner. 

367. Properties. — All of the chlorates, when exposed to moderate 
heat, undergo decomposition, and liberate oxygen most abundantly ; they 
are, therefore, generally used for the production of oxygen (§ 281). "When 
thrown upon ignited charcoal, the chlorates deflagrate with scintillations, and 
when heated with substances which have a strong attraction for oxygen, such 
as phosphorus and sulphur, they explode violently (§ 285). Mere friction, 
also, with these elements is sufficient to cause a detonation ; for example, if a 
half a grain of sulphur be triturated in a mortar with two or three grains of 
chlorate of potash, the friction is attended with a series of small explosions. 
A mixture of chlorate of potash, sulphur, and a little charcoal, was formerly 
used as a percussion powder for gun-caps ; but its action upon the locks was 
found to be highly corrosive. 

Paper soaked in a solution of a chlorate, burns in the same manner as touch- 
paper. 

An attempt was made by the French government, toward the close of the 
last century, to substitute chlorate of potash in place of niter (saltpeter) in the 
manufacture of gunpowder ; but the liability to accidental explosion was so 
greatly increased, that the enterprise was speedily abandoned. It is, how- 
ever, still used to a very great extent in the manufacture of fire-works, and 
especially in the production of colored fires. 

368. Peroxyd of Chlorine, C10 4 . Hypochloric Acid. — This sub- 
stance, which can not be obtained in a state of purity without great danger, 
is prepared by distilling chlorate of potash with strong sulphuric acid. It is a 
gas of a yellow color, which is gradually decomposed by the influence of light, 
and at a temperature less than that of boiling water, its elements separato 



Questions. — What are Labarraque's and Burnet's disinfecting fluids ? "What is said of 
chloric acid? How is chlorate of potash prepared? What are the properties of the 
chlorates ? For what purposes are they practically employed ? What is said of peroxyd 
of chlorine ? 



248 INORGANIC CHEMISTRY. 

with a most violent explosion. Mere contact with many combustible matters 
also occasion an immediate explosion. 

Some of the properties of this singular compound may be experimentally 
illustrated without danger. If a few grains of loaf sugar and chlorate of pot- 
ash be separately pulverized, and mixed together in equal proportions, with- 
out friction, the addition of a single drop of sulphuric acid, let fall from the 
end of a glass rod, will produce instantaneous and brilliant deflagration. The 
chemical reaction which occasions this result is as follows : The sulphuric 
acid decomposes the chlorate of potash, and liberates peroxyd of chlorine; 
this, in turn, by contact with the sugar, is decomposed, and evolves heat suf- 
ficient to produce combustion. 

Another very brilliant experiment consists in bringing phosphorus in contact 
with peroxyd of chlorine under water at the very instant of its development. 
A deep glass vessel being chosen (a conical wine-glass will answer), a few 
small pieces of phosphorus are first thrown in, and the glass two thirds filled 
with water. Crystals of chlorate ot potash, about equal in quantity to the 
phosphorus employed, are then allowed to fall through the water and settle 
upon the phosphorus. All that now remains to be 
done is to bring sulphuric acid in contact with the two, 
which is easily accomplished by means of a dropping- 
tube, or small glass tube and funnel — the extremity 
ot either of which being brought in contact with the 
mixture, the sulphuric acid is caused to touch the 
solids, without mixing with, and suffering dilution by, 
the water. (See Fig. 119.) Peroxyd of chlorine being 
rapidly evolved, the phosphorus reacts upon it, and 
flashes ot a beautiful green light under water, attended 
with a crackling noise, are produced. 

The two other principal compounds of chlorine with 
oxygen, chlorous and perchloric acid, although of scientific interest, are of no 
practical importance. 

369. Chloride of JVitroge n. — The single compound which chlorine 
is known to form with nitrogen, is especially worthy of note as probably the 
most dangerous of all chemical combinations. 

"When a bottle of chlorine, perfectly free from greasy matter, is inverted 
over a leaden dish containing a solution of 1 part of sal-ammoniac (NH4CI) in 
12 parts of water — the mouth of the bottle slightly dipping beneath the sur- 
face — drops of an oily-looking substance will gradually form upon the liquid 
and fall to the bottom of the dish, — chlorine slowly disappearing. The fluid 
substance thus generated is chloride of nitrogen. During the whole opera- 
tion, the bottle must not be approached, unless the face is protected by a wire- 
gauze mask, and the hands by thick woollen gloves. The leaden dish con- 
taining the chloride of nitrogen, may, after a time, however, be withdrawn 

Questions. — How may its properties be illustrated ? What is said of chloride of nitro- 
gen ? How is it prepared ? 




CHLORINE. 249 

from under the bottle, care being taken to avoid all agitation and contact with 
the glass. 

As thus prepared, it is a volatile, oily liquid, with a peculiar, penetrating 
odor. When heated to about 200° F., or when merely touched with a greasy 
substance, with phosphorus or an alkali, or even when subjected to the slight- 
est friction or jarring, it explodes with a flash of light and a violence that is 
difficult to conceive of. Glass and cast-iron in proximity to it, are shattered 
into fragments, and a single drop has been known to cause a perforation 
through a thick plank. A leaden vessel yields to its effects, and is merely 
indented. 

The chemical constitution of this body is not certainly known ; neither are 
the principles involved in its remarkable reactions at all understood. Sim- 
ilar compounds of nitrogen may also be formed with iodine, bromine, and cy- 
anogen. _. J 

370. History of Bleach in g. — The past history and present condi- 
tion of the great industrial art of bleaching appropriately connects itself with 
the subject of chlorine. Before the discovery and application of this element, 
the operation of bleaching cotton and linen consisted essentially in washing 
and boiling the fabrics in hot water, with soap and alkalies, and subsequently 
exposing them for a lengthened period on the grass to the action of light and 
air. These operations were successively repeated, and the time required to 
render a piece of linen white and suitable for market, varied from four to 
eight months. During the 16th and 17th centuries, the Dutch enjoyed an 
almost complete monopoly of the business, and almost all the linen goods f P 
manufactured in Europe were sent to Holland to be bleached. The Dutch 
affixed their imprint on all goods bleached by them, which were afterward 
known as " Hollands," a term applied to linens even at the present day. 

This method of bleaching was extremely expensive, not only on account of 
the time and labor required in the operation, but also from the great extent 
of grass-land necessary for the spreading of the cloths. Goods thus exposed 
out-of-doors served as a temptation to dishonest persons, and the old statute 
laws of England abound in severe penalties against trespassers upon bieach- 
fields. 

The decolorizing action observed to take place when organic products are 
exposed to the action of light, air, and moisture, is explained on the same 
general principles, as in the case of chlorine (§ 354); viz., the coloring com- 
pound is broken up by the abstraction or union of its hydrogen constituent 
with the oxygen of the air, or with the oxygen contained in dew and aqueous 
vapors, it being a fact that "grass-bleaching" is most rapid at those seasons 
and times when the deposit of dew is most copious and abundant. It is also 
probable that the ozone present in the atmosphere exerts some effect, and 
the chemical action of light is known to be essential, inasmuch as the bleach- 
ing will not take place in the dark. 

Qttebtioxs. — What are its characteristic properties? What was the original method 
of bleaching? What is said of the early history of bleaching ? 



250 INORGANIC CHEMISTRY. 

One of the improvements in bleaching introduced by the Dutch was that of 
souring," which consisted in steeping the goods for a considerable length of 
time in sour milk; but about the year 1750, very dilute sulphuric acid was 
substituted in its place. This simple change was a most important discovery, 
inasmuch as it shortened the time required for bleaching linen by nearly three 
months, and greatly reduced the expense. In fact, the operation of " souring" 
by sulphuric acid still forms an essential feature of the modern processes of 
bleaching. 

In 1785, Berthollet, a French chemist, while repeating some experiments on 
chlorine, which had been discovered by Scheele in 1774, ascertained that a 
solution of this gas in water was capable of destroying vegetable colors, and 
he was hence led to suggest its application to bleaching. About this time 
Berthollet was visited by James Watt, of England, celebrated from his connec- 
tion with the steam-engine, to whom he related the results of his experiments. 
Watt, on his return to England, practically examined the subject, and made 
a successful trial of bleaching with the new agent, at an establishment near 
Glasgow, Scotland. From thence its use rapidly extended throughout Great 
Britain. 

The introduction of chlorine as a bleaching agent, like all other great dis- 
coveries which tend to overturn old practices, encountered a most strenuous 
opposition. 

The first method of using it, consisted in saturating cold water with 
the gas, and immersing the goods to be bleached in the solution. Heat 
being applied, the chlorine was evolved from the water and acted upon the 
coloring matters. The difficulties which attended this procedure were, that 
the gas was evolved so abundantly, that the workmen were unable to endure 
it, and the strength of the cloth also was impaired. A defect of the goods, 
becoming yellow after some days, led to the operation of boiling in alkaline 
leys, when it was discovered that solutions of the alkalies not only absorb a 
greater quantity of chlorine than water, but hold it with greater affinity — not 
allowing the gas to escape and affect the atmosphere, but at the same time 
imparting it regularly and effectively to fabrics in contact with them. The 
knowledge of these facts prepared the way for the further discovery, in 1798, 
by Mr. Tennant, of Scotland, of the compound known as " chloride of lime," 
or "bleaching-powder," the manufacture of which has been already described 
(§ 365).* During all this period the constitution of the bleaching agent in 



* Chlorine, in its combination with lime, is completely under the control of the manu- 
facturer, and can be used with any amount of violence, so to speak, within the limits of 
its powers. It may be developed at once, if desired, or its evolution can be effected by 
the slowest degrees. It is possible to so dilute bleaching-powder with water, that it shall 
exercise no bleaching effect of itself, but this effect shall be developed by the disturbing 
action of a third substance. This may be illustrated by making an exceedingly dilute 

Questions. — What improvement was introduced by the Dutch ? What was the next 
advance in the art? What did Berthollet discover? What followed Berthollet's discov- 
ery? What was the first method of bleaching by chlorine ? What difficulties were en- 
countered ? How were they overcome ? 



ft 

-.. 7C- 

CHLORINE. 

question was unknown, it being regarded as a compound containing oxygen, 
termed " oxy -muriatic acid;" and it was not until 1811 that Sir Humphrey 
Davy demonstrated its true elementary character, and called it chlorine. 

Some idea of the wonderful results which have flowed from the discovery 
and practical application of chlorine may be formed from the following facts : 
bleaching operations, which less than one hundred years ago, required from 
four to eight months, are now accomplished in comparatively few hours ; the 
quantity of cloth bleached by several of the large establishments of England 
and the United States ranges from twenty to fifty thousand yards per day; 
and it has been further estimated that all the available labor of the civilized 
world would at the present time be insufficient to supply, by the old process, 
the present demand and consumption of bleached cottons and linens. 

The operations of a modern bleachery for cotton fabrics may be briefly de- 
scribed as follows: — "All cotton fibers are covered with a resinous substance, 
which, to a certain extent, prevents the absorption of moisture, and also with 
a yellow coloring matter, which, in some kinds of cotton, is so marked as to 
give a distinctive character to the fabric made from it, as in nankeen, which 
is manufactured in China from a native brown cotton. In some varieties of 
cotton the quantity of coloring mater is so small that the fabric would not re- 
quire bleaching were it not for the impurities acquired in spinning and weav- 
ing." 

The first process of bleaching is called " singeing," and consists in passing 
the cloth with great rapidity over a red-hot copper cylinder. This burns, or 
" singes" off the fibrous down or " nap" from the surface of the cloth, render- 
ing it smooth and more suitable for the reception of colors, in subsequent 
operations of dyeing and calico printing. 

After singeing the goods are placed in large hollow wheels, each of which 
has four compartments, with openings upon its face. (See Fig. 120). Water 
being admitted into the compartments by means of apipe concentric with the 

solution of chloride of lime in water ; bo dilute that a solution of indigo poured into it is 
not perceptibly decolorized. If -we now add a third or disturbing agency, in the form of 
a few drops of acid of any kind, chlorine is liberated, and decoloration takes place. A 
very beautiful application of this property is made in calico-printing. Suppose it is de- 
sired to produce a white pattern on a colored ground — white dots or leaves, for example, 
on a field of bright red, the red being a color removable by the agency of chlorine — this re- 
sult is effected by the following course of manipulation : The whole fabric is first dyed of 
a uniform color, and then the form of the desired pattern i3 compressed upon the cloth 
with stamps coated with some substance containing a very weak acid. An acid known as 
citric acid (a crystalline solid), mixed with gum, is generally used for this purpose. The 
fabric is now dried, and still exhibits an uniform color. No sooner, however, is it dipped 
in a weak solution of chloride of lime, than the citric acid sets up just that amount of local 
decomposition necessary to affect the liberation of the chlorine, which immediately 
bleaches out the stamped pattern, leaving the unstamped portions of the fabric unchanged. 
The material which thus effects the liberation of chlorine, is termed a mordant, and the 
operation is called '■'■mordanting.'" — Faeaday. 

Questions. — Enumerate some of the results which have followed the discovery and 
application of chlorine. What is the natural state of cotton fibers ? What are the suc- 
cessive operations of a modern bleachery ? 




252 



INORGANIC CHEMISTRY. 



axis, the wheel is caused to rotate rapidly, and the cloth, toy agitation and 
dashing of the water, is speedily and thoroughly washed. 

Fig. 120. 




The next operation consists in boiling the cloth in an alkaline solution, 
which removes all the greasy and resinous matters. This is effected' hrarps 5 - 
culiar manner ; the doth is placed in large vats, on a grating, or perforated 
false bottom, through which, from a compartment below, rises a pipe, furnished 
on its extremity with a curved iron cover. (See Fig. 121.) A boiling solu- 
tion of alkali is forced, by steam pressure, from the compartment below the 
vat up through this pipe, and striking against the cover, is reflected upon the 
goods in the form of a shower ; thence filtering through the texture of the 
cloth, the liquor runs back into the lower compartment, to be again heated by 
steam, and forced up as before. This process is continued for about seven 
—hours, and at its conclusion the color of the cloth is darker than at the out- 
set. The -cloth JU then washed again in the wheels, and next steeped in a 
very dilute solution of chloride of lime, in darge vats, for about six hours; 
it even then is not white, but of a gray appearance. 

In the next process, the goods arc steeped for four hours in very dilute 
sulphuric acid, when a minute disengagement of chlorine takes place through- 
out the substance < f the cloth, and it immediately assumes a bleached ap- 
pearance. The same operations of washing, boiling, bleaching, and souring, 
are then successively repeated, in less time, until at length the cloth is perfectly 
whitened. 

The length of time required for all these operations is from 24 to 48 hours ; 
one parcel of goods succeeding another in each successive stage of the pro- 



CHLORINE 



253 



cess, so that all the departments of a bleachery are in full operation at the 
same time. The labor of handling the cloth, which may seem very great, is 
nearly all performed by machinery, with great rapidity, at a very slight ex- 
pense — the average cost of bleaching cotton fabrics not exceeding one cent 

Fig. 121. 




per yard. Cottons subjected to bleaching lose about 10 per cent, in weight. 
Wool is bleached by washing, and exposure to the vapor of burning sulphur. 

SECTION VI. 

IODINE. 

Equivalent, 127. Symbol, I. Specific gravity of vapor, 8'7. 

371. History.— Iodine was discovered in 1811 by M. 
Courtois, a chemical manufacturer of Paris. 

He noticed that a dark-colored liquor, left after the preparation of soda 
from the ashes of sea-weeds, powerfully corroded his kettles, and that when 
sulphuric acid was added to the liquor, a brown substance separated, which 
on the application of heat was converted into a violet-colored vapor. A sub- 
sequent examination showed that the substance in question was a new ele- 
ment — Iodine. 

***. Natural History — Iodine is widely, but sparingly distributed 
in nature. In the inorganic kingdom it is a constituent of all sea-water, of 
many mineral springs (Saratoga, Carlsbad, etc.), and also of certain rare min- 
erals. In the organic kingdom, it exists probably in all marine plants, but 



Questions. — "When and by whom was iodine discovered? What circumstances led to 
its discovery ? What is said of its distribution in nature ? 



254 INORGANIC CHEMISTRY. 

more abundantly in some species than in others ; also in sponges, in tho 
oyster and other sea-mollusks, and in some fishes (i. e., cod-fiver oil). It is 
always found in combination with other substances — generally as iodide of 
sodium, or magnesium. 

372. Preparation . — The greater part of the iodine of commerce is 
manufactured at Glasgow, from "kelp," which is the ashes of sea- weeds col- 
lected and burned upon the coasts of Scotland and Ireland. The kelp is 
treated with water, which dissolves out a large quantity of soluble saline 
matters — carbonate of soda, common salt, chloride of magnesium, etc. When 
these substances are separated from the solution by partial evaporation and 
crystallization, there remains behind a dark-colored liquor, which contains 
iodine. This is heated with sulphuric acid and peroxyd of manganese, when 
the iodine distils over as a purple vapor, which is collected in receivers and 
condensed to a solid by cooling. A ton of kelp yields 9 pounds of iodine. 
The chief uses of iodine are for medicine, photography, and to some extent in 
dyeing. 

373. Properties . — Iodine, at ordinary temperatures and pressures, is 
a solid, and is generally obtained by crystallization in the form of bluish-black 
scales, which possess a brilliant and somewhat metallic luster. Exposed to 
heat, it liquefies at 225° F., and boils at 350°, forming a magnificent purple 
vapor, from whence it derives its name (ludr/g, violet-colored). This property 

-p 199 may be beautifully illustrated by heating a few grains of 
iodine in a glass flask, or test tube, over a spirit-lamp. (See 
Fig. 122.) On withdrawing the heat the vapor condenses, 
and forms brilliant crystals of solid iodine upon the sides of 
the flask. 

Dropped on a red hot surface iodine melts, and as a liquid 
assumes the spheroidal state (§ 154), forming a splendid ex- 
periment. 

Iodine, when taken inwardly, acts in large doses as an ir- 
ritant poison ; but in small quantities it is a most valuable 
medicine. Long before its discovery, the ashes of a burnt 
sponge were often prescribed as a most efficacious remedy for 
certain diseases. Their effect is now known to have been 
due to the iodine contained in them. Iodine stains the skin and most or- 
ganized substances of a brown color, and gradually corrodes them. Water 
forms with it a yellow solution, but dissolves it only in very small quantity — 
1 part in 7,000. Its bleaching properties are very feeble. Alcohol, ether, 
and solutions of the salts of iodine, dissolve it freely. 

374. Iodine attacks the metals rapidly. Iron or zinc placed in water with 
it are readily dissolved, an iodide of the metal being formed. Some of the 
combinations of iodine with the metals are remarkable for their brilliant 



Qtjestioxs. — How is it prepared ? What are its properties ? From what circumstance 
does it derive its name ? What are the effects of iodine upon the animal system ? What 
is said of its combinations with the metals ? 




BROMINE. 255 

colors. An illustration of this forms an easy and striking experiment. Place 
in three test tubes a solution of iodide of potassium in water ; if we add to 
the first a few drops of a solution of mercury (corrosive sublimate), we ob- 
tain a beautiful salmon-colored precipitate, which almost immediately changes 
to scarlet. A solution of sugar of lead added to the second, produces a bright 
yellow precipitate ; and a solution of subnitrate of mercury added to the 
third, a green precipitate. 

The distinctive test for iodine is a solution of starch, with which it strikes 
a deep blue color. The solution must, however, be cold, and no alkali must 
be present. This may be illustrated by experiment as follows : — Draw or 
paint upon a sheet of paper, figures in starch paste, and expose the paper to 
the vapor arising from iodine thrown upon a hot surface. The figures, which 
were before colorless, immediately become blue. If a little of the tincture of 
iodine be dropped upon flour, potatoes, etc., the presence of starch in these 
bodies will be indicated. 

Iodine unites with hydrogen to form an acid, hydriodic acid, HI, and with 
oxygen, in several proportions, to form both oxyds and acids. Its principal 
oxygen compound is iodic acid, IO5. 

The most important compound of iodine is that which results from its union 
with potassium, forming a white crystallizable salt, the iodide of potassium, 
also termed the " hydriodate of potash" (KI). It is in this condition that 
iodine is chiefly used in medicine, and also in photographic operations. 



7 



SECTION YII. 

BROMINE. 

Equivalent, 80. Symbol, Br. Specific gravity 0/ vapor, 5*3. 

375. History — Bromine was discovered by M. Ballard, 
a French chemist, in 1826, in the " mother/' or residual 
liquor left after the crystallization and separation of the 
salts of sea- water. 

376. Distribution . — It exists in all sea- water in minute quantity, 
generally in the proportion of about one grain to the gallon ; and for the 
most part in combination with magnesium, forming bromide of magnesium. 
It is also found in certain mineral springs, and in a few minerals. 

377. Preparation « — Bromine is prepared by passing into the mother 
liquor of sea- water a stream of chlorine gas, and then agitating the liquor 
with ether. The chlorine sets the bromine free from its combinations, and 
the ether dissolves it. After standing for a little time, the etherial solution, 
having a fine red color, separates and floats at the top. 

378. Properties .—Bromine, at ordinary temperatures and pressures, 

Questions. — What is the distinctive test of iodine? What is the principal salt of 
iodine ? When and by whom was bromine discovered ? What is said of its distribution 
in nature ? How is bromine obtained ? What are its properties ? 



256 INORGANIC CHEMISTRY. 

is a red liquid, so deep in color as to be nearly opaque. It is extremely vola- 
tile, and can only be preserved in very close vessels. A few drops slightly 
warmed in a glass flask, will fill the vessel with blood-red vapors. Its odor 
is somewhat like chlorine, but more offensive ; hence the name Bpujuoc, lad 
odor. "When swallowed, it acts as a deadly poison, and a single drop upon 
the beak of a bird is said to occasion instant death. It rapidly destroys all 
organic tissues, and stains the skin permanently yellow. It boils at 145° F., 
and when exposed to a cold of — 10° F., freezes into a crystalline solid. 
Bromine bleaches like chlorine, is slightly soluble in water, but dissolves freely 
in alcohol and ether. It combines directly with many of the metals, and 
forms bromides — the act of combination being often accompanied with an ex- 
plosive evolution of light and heat. This may be experimentally shown by 
cautiously pouring a small quantity of powdered antimony or tin upon a few 
drops of bromine contained in a deep strong glass. In short, the properties 
of bromine greatly resemble those of chlorine, but they are less strongly 
developed. 

Bromine is extensively used in photographic processes, and sometimes in 
medicine. 

But one compound of bromine and oxygen is known, viz., bromic acid, 
BrOs ; it also unites with lryclrogen to form an acid, hydrobromic acid, HBr. 

SECTION" VIII. 

FLUORINE. 

Equivalent, 19. Symbol, F. Theoretical Density, 1*31. 

379. History, — Of this element but little is known 

except from its compounds. 

Its affinities for the other elements are so poweiful, and its action on the 
human system is so deleterious, that its isolation has been regarded as almost 
impossible. Within a comparatively recent period, however, several chemists 
have succeeded in separating it from all other bodies, in the form of a colorless 
gas. In its general nature and properties it undoubtedly resembles, and is 
closely allied to, chlorine, bromine, and iodine. 

The only compound in which it exists in nature in any abundance, is a 
compound of lime, called fluor-spar, or fluoride of calcium. This mineral is 
found, in great quantity and beauty, in Derbyshire, England, and from it 
the well-known ornaments known as "Derbyshire spar," are manufactured. 
Fluorine is also found in a great variety of other minerals, and exists in mi- 
nute quantities in the bones of animals, and in the enamel of the teeth. 

Compounds containing fluorine can be decomposed without difficulty, and 
the fluorine transferred from one body to another ; but so great is its affinity 
for the metals, and for silicon, a constituent of glass, that in passing out from 

Questions. — How does bromine act upon the metals? What are its uses? What its 
compounds ? What is known of fluorine ? What is said of its distribution in nature ? 
Why is it difficult to isolate fluorine ? 



FLUORINE. 257 

a state of combination, it combines again immediately with the material of 
the vessel containing it. 

3T9. 'Hydrofluoric Acid, HF.— Fluorine is not known to 
unite with oxygen under any circumstances, but with hy- 
drogen it forms a very remarkable compound, " hydroflu- 
oric acid." 

This substance is formed by heating powdered fluor-spar with strong sul- 
phuric acid, in a platinum or lead retort, furnished with a receiver of the same 
metal, which is kept cool by immersion in a freezing mixture. The chemical 
reaction which takes place may be expressed as follows : — 

Fluoride of calcium. Sulphuric Acid. Sulp. lime. Hydrofluoric acid. 

CaF -f- SOs HO — CaO, S0 3 + HF 

The acid thus obtained is a gas at ordinary temperatures, but is condens- 
ible by cold into a volatile, colorless liquid, which evolves white, suffocating 
fumes on exposure to the air; its attraction for water is very great, and 
when poured into it, it hisses like a red-hot iron. As vapor, and as an 
aqueaus solution, it attacks and readily dissolves glass, and all compounds 
containing silica, together with some mineral substances that no other acid 
can affect. This property is often made available for etching upon glass. 

In its most concentrated form, hydrofluoric acid is a most dangerous sub- 
stance, and is more destructive of animal tissues than any other known agent. 
The most minute drop upon the skin occasions a deep and painful burn, often 
terminating in an ulcer difficult to cure. Its vapor is also in the highest de- 
gree corrosive. 

The peculiar action of hydrofluoric acid vapor upon glass may be easily illus- 
trated without danger, by the folio wing experiment. Place in a small leaden 
dish, or an earthen cup, the interior of which has been slightly oiled, a little 
powdered fluor-spar, and add strong sulphuric acid, Fig. 122. 

sufficient to form with it a thin paste. Cover the cup 
with a piece of window-glass which has received 
a coating of wax, and from some parts of which 
the wax has been removed, by scratching with a 
needle or other pointed instrument. (See Fig. 122.) 
After the lapse of some hours, remove the wax by 
melting and washing with oil of turpentine, when those parts of the glass left 
baro will be found to be deeply corroded. The same result can also be ob- 
t lined in the course of a few minutes, by a gentlo application of heat to tho 
cup containing the mixture. 



Questions. — What is its most remarkable compound ? How is it prepared ? What are 
its properties ? How does it act upon organic substances ? How may its action on glass 
be illustrated? 








258 INORGANIC CHEMISTRY. 

y 

SECTION IX. 

SULPHUR. 

Equivalent, 16. Symbol, S. Specific gravity, 1-98, in vapor, 6.65. 

380. Natural History and Distribution. — Sulphur is 
an element abundantly distributed in nature, most exten- 
sively as a mineral product, but widely and in small quan- 
tities as a constituent of animals and vegetables. It has 
been known from the most remote antiquity. 

Sulphur is found in a native, or uncombined state, in all volcanic districts ; 
and in Sicily and in some parts of South America, it exists in immense beds 
in the earth. Many of the compounds of sulphur with the metals occur as 
natural productions in great abundance, especially the sulphurets (sulphides) 
of iron, copper, lead, and zinc. The sulphuret of iron (iron-pyrites) is even 
employed as a source of sulphur. In an oxydized condition, as sulphuric acid, 
it is still more widely diffused in combination with various earths, as the 
sulphates of .lime, magnesia, baryta, etc. Nearly one half the weight of sul- 
phate of lime (g} r psum, or plaster of Paris) is sulphur. 

381. Most of the sulphur used in the arts is obtained from Sicily and the 
volcanic districts of southern Italy, the former exporting about 1,540,000 
cwts. yearly. It is generally subjected, on the spot where it is dug from the 
earth, to a rough purification by fusion, and is brought intocommerce in the 
form of amorphous, or semi-crystalline masses. Another commercial form is 
roll sulphur, or brimstone, which is generally the produce of roasting the 
sulphurets of iron and copper (pyrites), collecting the evolved fumes in con- 
densing chambers, and subsequently fusing the sulphur into sticks. " Flowers 
of sulphur," a powder, is a third commercial state which this element is made 
to assume ; and is produced by distilling sulphur and condensing the vapor. 

382. Properties . — Sulphur in its ordinary condition is a yellow, brit- 
tle solid, which, by warmth and friction, emits a characteristic odor (brim- 
stone odor). It is insoluble in water, and consequently tasteless ; it is very 
slightly soluble in alcohol and ether ; more so in oil of turpentine and somo 
other oils ; and readily in the bisulphide of carbon. It is a bad conductor of 
heat ; and a roll of sulphur, when grasped by the warm hand, crackles and 
frequently falls in pieces from unequal expansion. It is a non-conductor of 
electricity, but when rubbed develops negative electricity abundantly. 

Sulphur is highly inflammable, burning with a blue flame, and emitting 
suffocating fumes of sulphurous acid, (the familiar odor of a match). It has a 
powerful affinity for most of the other elements, and its act of combination " 

Questions. — What is the history of sulphur ? What is said of its distribution in na- 
ture? From whence are supplies of sulphur chiefly derived ? What are its commercial 
forms ? What are the properties of sulphur ? What is said of its solubility ? What of 
Its affinity for other elements ? 




SULPHUR. 259 

with the metals to form sulphides, or sulphurets, is often attended with an 
evolution of light and heat. This fact may be experimentally illustrated by 
placing in a flask a few fragments of sulphur, and above them some copper 
turnings; on the application of heat from a spirit-lamp, vapor of sulphur 
rises, and coming in contact with the copper, enters into vivid combination 
with it. 

383. Allotropism of Sulphur.— One of the most re- 
markable characteristics of sulphur is its allotropism, or 
power of existence in different states. 

The first indication of this power is perhaps to be found in the fact, that it 
is capable of assuming two distinct crystalline forms. These are not merely 
modifications of one original primary figure (to which cause most crystalline 
variations can be referred), but they belong to two different, in- p IG _ 123. 
convertible, and incompatible systems of crystallization, viz., 
oblique rhombic prisms and right rectangular prisms. Examples 
of the first form, Fig. 123, (octohedrons derived from oblique 
rhombic prisms), occur in native sulphur, or in sulphur crystal- 
lized from a solution. Examples of the second form may be ob- 
tained by melting a quantity of sulphur in an earthen crucible, 
and allowing it to solidify on the surface ; if the crust be then 

-j-, 1 „ . pierced with a hot wire, the fluid portion beneath may 

be poured off, when the interior of the crucible, on cool- 
ing, will be found to be lined with slender needles, or 
right rectangular prisms. (See Fig. 124.) 

Both forms of crystals may be obtained by dissolving 
sulphur in boiling oil of turpentine ; as the solution cools, 
the sulphur crystallizes out, first in the form of prisms ; 
but afterward, as the temperature is reduced, octohedrons 
are formed. 

The power possessed by sulphur of manifesting itself under two condi- 
tions, is, however, most strikingly illustrated by certain phenomena of its 
melting and subsequent cooling. Thus, if we heat a small quantity of sulphur 
in a glass flask over a spirit-lamp, it melts at a temperature of 250-280° F., 
into a clear, yellow liquid. If a portion of this liquid be poured into cold 
water, it immediately condenses into the state it had before melting — that is, 
into common, yellow, brittle sulphur. If to the portion remaining in the 
flask a stronger heat be applied (about 500° F.), the transparent fluid gra- 
dually thickens, becomes brown at first, and at last nearly black and 
opaque ; in this condition the viscidity of the sulphur is such, that the flask 
may be inverted without escape of its contents. If the heat be still further in- 
creased, the black, tenacious sulphur once more liquefies, though it never be- 



Qttestions. — What is said of the allotropism of 6ulphur ? What is the first indication 
of this property ? In what two forms does sulphur crystallize ? What are examples : 
In what other way may the allotropic properties of sulphur be illustrated? 




260 



INORGANIC CHEMISTRY 



comes as fluid as when first melted, at the temperature of 226° R, and if 
suddenly cooled, by pouring it in a slender stream into cold water, it -assumes 
a most singular state. It is no longer j'ellow and brittle, like ordinary sul- 
phur, or like tho product of pouring into water tho first result of fusion, but 
it remains soft, tenacious:, highly elastic, and of a brown color, resembling, in 
all its external characteristics, strips of India rubber or gutta percha. In this 
form it can bo molded by tho hand, and may bo used to take impressions of 
steals, medallions, etc. After the lapso of a little time, it again becomes yel- 
low, and returns to its original brittlo condition, giving out in tho transforma- 
tion a quantity of latent heat. ~^/ 

384. M i 1 k of S u 1 p Ii u r ,»^-If wc add to a strong boiling solution of 
potash or soda, a littlo of tho flowers of sulphur, a part of tho sulphur dis- 
solves, and imparts to tho liquor a yellowish-brown color. If a littlo of tho 
clear solution bo added to water, slightly acidulated, the acid will unite with tho 
alkali holding tho sulphur in solution, and cause tho sulphur to bo precip- 
itated in tho form of exceedingly minuto particles, giving to tho water a 
milky appearance. Sulphur in this form is nearly white in appearance, and 
is known as ' : Milk of Sulphur," or "Precipitated Sulphur." 

In tho organic kingdom sulphur is extensively, and perhaps universally 
diffused throughout animal substances, and exists in small quantities in 
most vegetables. Tho well-known blackening of a silver spoon immersed for 
somo timo in a boiled cgg 1 is duo to tho presence of sulphur in tho egg. Tho 
presence of sulphur also in a piece of flannel may bo strikingly demonstrated 
by immersing tho cloth in a mixture of oxyd of lead in a solution of potash ; 
on applying heat, tho flannel immediately turns black. 

385. Compounds of Sulphur and Oxygen . — Tho compounds 
of sulphur with oxygen aro numerous, but onhy two of them demand an ex- 
tensivo notico ; theso aro Sulphurous acid, S02, formed by the union of ono 

equivalent of sulphur with two of oxygen ; and 
Sulphuric acid, SOs, formed by tho union of ono of 
sulphur and three of oxygen. 

380. Sulphurous Acid, S O2 is form- 
ed when sulphur is burned in oxy- 
gen (See Fig. T25) or atmospheric air ; 
and is the occasion of the well-known 
suffocating odor of an ignited match. 
It exists in nature in the vicinity 
of volcanoes, and is often evolved 
in immense quantities from their 
craters. 



Yin. 1'25. 




QursTiONS— What is milk of sulphur? What is said of sulphur in the organic 
kingdom of nature? What arc illustrations of its presence in animal substances? 
What is said of the compounds of Sulphur with oxygen ? What of sulphurous acid ? 



SULPHUR 



261 



Fig. 126. 




When required in a puro state, it is best pre- 
pared by depriving oil of vitriol of a part of its 
oxygon. In order to effect this, two or threo 
ounces of concentrated sulphuric aeid aro boiled 
in a glass retort or Mask, with a half an ounce 
of copper turnings ; piecos of charcoal may bo 
substituted in placo of tho copper, but the gas 
evolved undor such circumstances is not pure. 
In this process, a part of tho aeid gives up one 
equivalent of its oxygen to tho metal, and 
sulphurous acid gas is libcratod ; tho oxyd 
of the metal produced, unites with a portion 
of undecomposod acid to form a sulphate. 
Thus:— 

Copper. Sulph. acid. Sulpli. eoppor. Sulphurous acid. 

Cu + 2S0 3 — CuO, S0 3 -f SO* 

By allowing tho gas to bubblo through water, a strong solution will bo ob- 
tained, which may bo used for illustrating tho properties of sulphurous acid. 

387. Properties . — Sulphurous aeid is a colorless gas, with a charac- 
teristic odor, easily condensible by cold or by pressure, into a colorless, limpid 
liquid. "Water, at 60° F., absorbs from 40 to 50 times its volumo of sulphur- 
ous acid, and forms thereby a strongly acid liquid. Hence it is necessary to 
collect this gas over mercury or by tho displacement of air from dry vessels. 
Its avidity for water is so great, that a pioco of ice introduced into a jar of 
it, is instantly liquefied. 

Sulphurous acid is not inflammable, and a lighted candlo immorscd in a 
jar of the gas, is immediately extinguished for tho want of frco oxygen. A 
most certain way of extinguishing a chimney on fire is to scatter flowers of 
sulphur on a pan of coals in a fireplace-opening beneath. Tho sulphurous 
acid gas formed by tho combustion of tho sulphur, ascends tho flue, expels 
the atmospheric air present in it, and by depriving tho burning soot of froo 
oxygen, extinguishes it. 

Sulphurous aeid possesses bleaching properties, and is oxtonsivcly employed 
in bleaching straw and wool. Tho articles aro moistened and suspended in 
closed chambers in which sulphur is burnod in an open dish ; (an inverted 
barrel is often mado to subservo tho purposo of a bleaching chamber.) Tho 
sulphurous aeid is absorbed by the damp goods, and discharges their color. 
Tho bleaching action appears to be duo to the fact, that the gas unites with 
the coloring matters to form colorless compounds. It docs not, like chlorine, 
decompose and destroy tho coloring matter, since by the action of a stronger 
chemical agent, tho colorless compound may be broken up and the original 



Qukstions. — How is it usually prepared ? Give the chemical reaction involved in its 
preparation. What are its properties f What are its relations to combustion ? How is 
Sulphurous acid employed in bleaching ? What is the nature of its bleachiug action ? 



262 INORGANIC CHEMISTRY. 

color restored. This may be illustrated by holding a red rose, or any other 
red flower, over a bit of burning sulphur. The color is speedily discharged, 
but may be again restored by washing with dilute sulphuric acid. White 
flannel which has been bleached by sulphurous acid, when washed for the 
first time with an alkaline soap, has its original yellow color in part restored 
to it. 

Sulphurous acid is also valuable as a disinfecting agent. 

The compounds of sulphurous acid with the bases are termed sulphites, 
hey are readily formed by transmitting a stream of gas through water in 
which the oxyd or the carbonate of the metal is dissolved or suspended, the 
carbonates being decomposed with effervescence. The sulphite of soda is 
known in commerce as antichlorine ; since its solution in water is able to 
neutralize the chlorine which may remain in fabrics after bleaching, and thus 
prevents its destructive action. 

388. Sulphuric Acid, S Oa. — This acid is one of the most impor- 
tant of all chemical reagents, and furnishes the means by which most other 
acids are prepared. Immense quantities of it are consumed in the manu- 
facture of carbonate of soda, nitric and hydrochloric acids, chlorine, alum, sul- 
phate of copper (blue vitriol), stearine, phosphorus, etc., and in dyeing, and 
in the refining of the precious metals. Its annual consumption in Great 
Britain alone is upward of twenty millions of pounds. 

389. Preparation . — It has been already stated, that when sulphur is 
burned in air, or oxygen, the product is sulphurous acid. This gas, if made 
to combine with half as much oxygen again as it already contains, is converted 
into sulphuric acid; thus S0 2 -f-0=S03. In other words, sulphurous acid 
must be oxydized in order to enable us to form sulphuric acid. Oxygen and 
sulphurous acid can not, however, be made to unite directly, but the inter- 
vention of some third substance is necessary. In the presence of water, the 
union takes place slowly, or if the two gases be mixed, and passed over 
spongy platinum, the union is effected immediately. 

Neither of these processes can, however, be used with advantage in tho 
arts; and the manufacture of sulphuric acid upon a large scale depends 
upon the fact, that when sulphurous acid mixed with oxygen is brought in 
contact with deutoxyd of nitrogen (NO2), or any of the other higher oxyds 
of nitrogen, combination takes place with great rapidity ; the presence of a 
very small proportion of deutoxyd of nitrogen being moreover sufficient to 
effect the combination of an almost indefinite amount of sulphurous acid and 
oxygen, provided that water is also present. 

The following experiment will serve to illustrate the general principle upon 
which sulphuric acid is manufactured. Burn in a jar, containing a little water 
at the bottom, a piece of sulphur ; as a consequence, the vessel becomes filled 
with sulphurous acid. If we now introduce into the gas a shaving moist- 

Questions. — What experiments are illustrative ? "What is said of the compounds of 
sulphurous acid with the bases ? What is antichlorine ? What is said of sulphuric 
acid ? What of its theoretical preparation ? Upon what fact does its practical preparation 
depend ? How may it be experimentally illustrated ? 



SULPHUR 



263 






I ^ : , ■ , - ^, 









ened with nitric acid, reddish-colored fumes will immediately form around the 
wood, and gradually fill the whole vessel. (See Fig. 127.) -piG. 127. 
These fumes are nitrous acid, and are produced by the ac 
tion of the sulphurous acid, which decomposes the nitric acid, 
and by depriving it of 2 equivalents of oxygen, becomes sul- 
phuric acid. Thus : 

Sulphurous acid. Nitric acid. Sulphuric acid. Nitrous acid. 

2S0 2 + N0 5 — 2S0 3 -f N0 3 . 
The vapor of the sulphuric acid formed is absorbed by the 
water in the jar, and by repeating the experiment several 
times, a quantity of dilute sulphuric acid may be prepared. 

On a large scale, the operation of manufacturing sulphuric acid is essen- 
tially the same in principle, and may be described as follows: immense 
chambers, lined with lead, are constructed ; in some instances 300 feet long, 

15 feet high, and 20 
broad. (See F^g. 128.) 
The floor of these cham- 
bers is covered to the 
depth of a few inches 
with water, and at one 
extremity there is ad- 
mitted by a suitable flue, B, sulphurous acid (from a furnace of burning sul- 
phur), with atmospheric air ; by another pipe, A, steam ; and by a third, C, 
vapors of nitric acid (obtained by heating nitrate of soda with strong sul- 
phuric acid). When these several substances meet within the chambers a 
most interesting and curious series of reactions take place ; — the sulphurous 
acid withdraws oxygen from the nitric acid vapor, JSTO 5 , and converts it into 
deutoxyd of nitrogen, N0 2 , itself changing into sulphuric acid, SO3. This 
last product then uniting with the steam, is precipitated to the bottom of the 
chamber, and is absorbed by the water. The deutoxyd of nitrogen does not 
remain unaltered, but in contact with the air admitted into the chambers, 
absorbs two equivalents of oxygen, and becomes converted into peroxyd of 
nitrogen, NO4, forming red fumes (§ 347). These in turn, by contact with 
the sulphurous acid, give up their newly-acquired oxygen to form sulphuric 
acid, and are reconverted again thereby into deutoxyd of nitrogen. And 
this process is repeated over and over again, a small quantity of deutoxyd of 
nitrogen acting as the intermediate agent for withdrawing oxygen from the 
air, first to itself, and afterward giving it up to oxydate the sulphurous acid. 
The deutoxyd of nitrogen, together with the remaining nitrogen of the air, 
is finally allowed to escape at the further extremity of the chambers, and a 
fresh portion of nitric acid vapor is admitted to supply its place, and com- 
mence the reactions anew. The steam admitted into the chambers does not 
take any active part, but its presence is essential to the success of the opera- 1 



Questions.— How is the practical manufacture conducted ? What reactions take place 
in the leaden chambers ? 



264 INORGANIC CHEMISTRY. 

tion.* The chambers in which the acid is manufactured are usually divided 
into partitions, in order that the gases may mix together slowly and com- 
pletely, before reaching an exit tube placed at the further extremity. • 

The sulphuric acid which collects in the water at the bottom of the cham- 
bers, is drawn off when it reaches a specific gravity of about 1*5 ; it is, how- 
ever, in this state too dilute for sale, and is accordingly evaporated by heat in 
shallow lead pans, until it becomes strong enough to corrode the lead, when 
it is transferred into glass or platinum retorts, f and further heated until it 
attains a specific gravity of T84. In this condition it constitutes the con- 
centrated oil of vitriol of commerce, and is transported in carboys, or largo 
glass bottles packed in boxes. As thus produced, it is a definite hydrate, 
composed of 1 equivalent of acid, and 1 of water (SO3, HO). This proportion 
of water, amounting to three ounces in every pound of acid, is held so firmly 
that it can not be driven off by heat. (See § 322.) 

390. Nordhausen Sulphur ic Acid . — In early times sulphuric 
acid was obtained by distilling dry sulphate of iron (green vitriol) in earthen 
retorts, at a high temperature. As thus prepared, it is a dark-brown, thick, 
oily liquid, and was originally called, from its derivation, " oil of vitriol." It 
is the most concentrated form in which sulphuric acid can exist in a fluid 
condition, and contains less water than the ordinary concentrated sulphuric 
acid. When exposed to the air it fumes, and when dropped into water, 
hisses like a red hot iron. As acid in this state of concentration is required 
for certain processes in the arts, it is still prepared in the old way, especially 
at the town of Nordhausen, in Saxony, Germany; — hence its commercial 
name. 

Sulphuric acid is known to combine with water in four proportions, forming 
four definite hydrates. Their composition may bo illustrated as follows : — 

Nordhausen acid, sp.gr 1-9 2(S03)HO 

Oil of vitriol, " 1-84 SOs,HO 

Sulphuric acid of " 1-78 S03,HO + HO 

" " " 1.63 S03,HO + 2HO(§274.) 

* The description of the chemical changes involved in the manufacture of sulphuric acid 
in the leaden chambers, as thus given, is but an outline, embracing merely the funda- 
mental principles. For the minute details, not suited for an elementary work, the stu- 
dent is referred to any of the modern encyclopedias of practical science. 

t It was originally the custom to concentrate the sulphuric acid by boiling it in glass 
vessels, but the loss from breakage is so great, that in many manufacturing establish- 
ments platinum stills have been adopted, this metal resisting the action of the strongest 
acid at high temperatures. These stills are constructed in Paris of thin sheets of platinum 
soldered with gold. They are oval in form ; and as a protection against the direct action 
of heat, they are inclosed in iron jackets. Their capacity varies from 500 to 2,000 pounds, 
and their cost from $S,000 to $13,000 apiece; and although one of these vessels only en- 
dures for a period of two or three years, their use has proved more economical than 
glass. 

Questions What is the density of the acid thus formed ? To what processes is it 

subjected ? What is the composition of concentrated oil of vitriol ? What is Nordhausen 
sulphuric acid ? What are its properties ? How many hydrates of sulphuric acid are 
known ? 



SULPHUR. 265 

591. Anhydrous Sulphuric Acid . — When Nordhausen acid is 
carefully distilled in a retort furnished with a receiver kept cool by a freezing 
mixture, white fumes pass over, which may be condensed into a white, silky- 
looking, fibrous mass — anhydrous sulphuric acid. This substance possesses 
no acid properties, and may be handled without danger. When thrown 
into water, it hisses, and forms liquid sulphuric acid. It also liquefies on 
exposure to air, by the absorption of moisture. 

392. Properties . — The oil of vitriol of commerce is a dense, oily-look- 
ing liquid, without odor, and of a brownish color. It is the strongest of all 
acids. It freezes at a temperature of — 29° F., and boils at 620° F. Its affin- 
ity for moisture is most intense, and it abstracts it from every substance with 
which it is brought in contact. If a quantity of strong sulphuric acid be ex- 
posed in a shallow dish to the air, it frequently absorbs sufficient aqueous 
vapor from the atmosphere to double its weight. A piece of wood introduced 
into sulphuric acid becomes black and reduced to coal, the same as if it had 
been exposed to the action of fire. The explanation of this is as follows : the 
wood is a compound of oxygen, hydrogen, and carbon ; the sulphuric acid 
abstracts the oxygen and hydrogen, which combine to form water, while the 
carbon remains behind. Gases containing aqueous vapor are deprived of it 
by causing them to bubble through strong sulphuric acid. 

"When concentrated sulphuric acid is mixed with water, great heat ig 
evolved, and the mixture, when cold, occupies less bulk than the two liquids 
did separately. This fact maybe strikingly illustrated -^ ,„„ 

by mixing 4 parts of oil of vitriol with 1 of water. Water 
in a test tube immersed in such a solution, may be caused 
to boiL (See Fig. 129.) 

Sulphuric acid does not evaporate at the ordinary tem- 
perature of the air ; but if a drop of dilute acid fall upon 
a cloth, the water gradually evaporates until the acid 
which is left behind acquires a considerable degree of 
strength, and then chars or destroys the cohesion of the 
fibers; hence the destructive action of sulphuric acid 
upon fabrics even when very much diluted. — Miller. 

Ordinary sulphuric acid is never pure, but always contains lead derived 
from the leaden chambers ; when mixed with water, this lead is precipitated, 
and causes the solution to appear milky. 

Sulphuric acid attacks all the metals except gold, platinum, iridium, and 
rodium. 

393. Hyposulphurous Acid, S 2 2 . — By digesting sulphur with 



Questions. — What is anhydrous sulphuric acid ? What are its properties ? What are 
the properties of " oil of vitriol?" What is said of its attraction for moisture? What 
are illustrations of this ? When concentrated sulphuric acid is mixed with water, what 
follows ? What is said of the action of sulphuric acid on fibers ? What of its purity ? 
What of its action on metals? What is said of hyposulphurous acid and its com- 
pounds? 




266 



INORGANIC CHEMISTRY. 



a solution of sulphate of soda, a portion of the sulphur is dissolved, and a salt 
containing hyposulphurous acid is formed — the hyposulphite of soda. The 
acid itself can not be isolated. Hyposulphite of soda is at present largely 
employed in photographic operations, owing to its property of dissolving cer- 
tain salts of silver which are insoluble in water. The surface of the photo- 
graph is freed from them by immersion in a solution of it ; after which, if well 
washed with water, it is no longer liable to alteration by exposure to light. 

394. Sulphur and Hydrogen. 

Hydro sulphuric Acid, HS. — Sulphuretted Hydrogen, 
Sulphydric Acid. — This gas is formed naturally during 
the putrefaction of many organic substances, and is also a 
constituent of many mineral springs. It is easily prepared 
by the action of dilute sulphuric_acid upon jjrotosulphide 
of iron, Ee&S 



Fig. 130. 



Fig. 131. 



For this purpose an evolution flask (Fig. 130) is best 

adapted ; but a common, open-mouthed bottle, fitted with a 

perforated cork and bent tube, will 

answer. (See Fig. 131.) Introduce 

into the flask protosulphide of iron in 

small quantities, with water sufficient 

to cover it ; then add sulphuric acid 

until a copious disengagement of gas 

takes place. By introducing the evolu- 
tion tube into cold water, a solution of 

the gas will be obtained, in which state its properties may be ex- 
perimentally illustrated to the best advantage. The operation of preparing the 
gas should be conducted in a well-ventilated apartment, or in the open air. 

The chemical reaction involved in this operation is as follows : water is de- 
composed ; its oxygen uniting with the iron to form oxyd of iron, which 
dissolves in the acid to form sulphate of iron, while the hydrogen escapes, and 
takes with it the sulphur contained in the sulphide of iron. Thus : — 

Sulphide of iron. Sulphuric ncid (dilute). Sulphate of iron. Hydrosulph. acid. 





395. 



FeS + S0 3 , HO = FeO, S0 3 + HS. 
Properties . — Hydrosulphuric acid is a transparent, colorless gas, 



of a disgusting odor, like that of rotten eggs. It is about one fifth heavier 
than common air, and burns with a blue flame, with a smell of sulphur. It 
is highly poisonous when respired in a concentrated form, and even when 



* Protosulphuret of iron is prepared by heating 2 parts of iron filings with 1\ parts of 
sulphur, to a red heat, in a covered earthen crucible. 



Questions. — What of hydrosulphuric acid ? How is it prepared ? What chemical re- 
actions are involved in its preparation ? What is said of its properties ? "What of its 
poisonous effects? 



SULPHUR. 267 

present in. the air in very minute proportions, it is rapidly fatal to the lower 
orders of animals. A single gallon of it, mixed with 1,200 of air, will render 
it poisonous to birds, and 1 in 100 will kill a dog. When inhaled it acts di- 
rectly upon the blood, thickening it, and turning it black. It is this gas which 
makes an open or foul sewer so destructive of health to any district in which 
it may be situated. When present in the air of a room, it may be instantan- 
eously destroyed by the action of a small quantity of free chlorine. A cloth 
moistened with alcohol, and held before the mouth, is a good protection also 
against its inhalation. 

By pressure, sulphuretted hydrogen is reduced to a colorless liquid, which 
freezes at — 122° F. into a crystalline, semi-transparent mass. Cold water 
dissolves between two and three times its bulk of this gas, producing a feebly 
acid liquid, which possesses the characteristic smell and taste of sulphuretted 
hydrogen, with all its properties. When exposed to the air, this solution be- 
comes milky ; the hydrogen being slowly oxydized to form water, while the 
sulphur separates. The solution, therefore, should be kept in well-stopped 
bottles, quite full. 

Sulphuretted hydrogen is formed naturally under a variety of circumstances. 
Its chemical proportions being 1 equivalent of hydrogen (1) to 1 of sulphur 
(16), it follows that 100 parts of the gas contain only about 6 parts of hy- 
drogen ; so that a very small proportion of hydrogen causes a large amount 
of sulphur to assume with it an aeriform condition, and exhibit the foetid odor 
and poisonous properties of the gas in question. In volcanic countries sul- 
phuretted hydrogen is often evolved from fissures in the rocks, mixed with 
steam and other gases ; in sewers and cesspools it is produced in large quan- 
tities by the decay of organic matter, and in marshes, where vegetable mat- 
ter alone is undergoing decay, in the presence of water containing sulphate 
of lime (gypsum), its presence may be often detected. The waters of mineral 
springs, as those of Avon and Sharon, N. Y., and the sulphur springs of 
Virginia, often contain sulphuretted hydrogen, though rarely in a proportion 
exceeding 1£ per cent, of their volume ; and the gas in solution in this small 
quantity, when taken into the stomach, acts as a valuable medicinal remedy 
for various diseases. 

Hydrosulphuric acid, though a feeble acid, combines readily with bases to 
form sulphides, or sulphurets. Thus, if we place a drop of sulphuretted 
hydrogen water upon a bright silver or copper coin, or upon a piece of lead, 
a black spot will be quickly produced, owing to the formation of a black 
compound of the metal and sulphur (a sulphide). The black sulphide of lead 
formed when hydrosulphuric acid is brought in contact with the salts of lead, 
is particularly noticeable, and may be exhibited by exposing a piece of paper 
moistened with acetate of lead to air impregnated with this gas. This test is 
so delicate, that 1 part of sulphuretted hydrogen in 20,000 of air is said to 



Questions.— What is said of the solubility of this gas ? "What of its natural formation 
and proportional composition ? What is said of its presence in mineral springs ? What 
of its combinations with, the metals ? 



268 INORGANIC CHEMISTRY. 

be sufficient to occasion a blackening of the paper. For the same reason, 
surfaces covered with lead paints, in the vicinity of sewers, cesspools, or the 
bilge- water of vessels, etc., soon become discolored. Sulphur unites with zinc 
in the same manner as with lead, but the resulting compound, sulphide of 
zinc, is white, and not dark colored like the sulphide of lead. Hence zino 
paints, for many locations, are more suitable than lead paints. 

"When hydrosalphuric acid, either in the form of gas or solution, is added 
to a solution containing copper, silver, gold, lead, tin, antimony, or arsenic, 
these metals are precipitated as insoluble sulphides, and may be collected and 
separated from the solution by filtration. If iron, zinc, manganese, cobalt, 
and nickel are contained in the same solution, they are not precipitated until 
a stronger reagent is added. Hence sulphuretted hydrogen may be used to 
separate one class of metals from another ; and in fact is employed extensively 
for this purpose in chemical analysis. 

SECTION X. 

SELENIUM AND TELLURIUM. 

396. Selenium, Se . — This element was discovered by Berzelius in 
1817, and was named by him Selenium, from 'Lelrjvrj, the moon. It is one of 
the least abundant of the elements, and always occurs in combination, gen- 
erally in ores of iron, copper, and silver, forming selenides of these metals. 
The principal localities in which it exists are in Norway, Sweden, and the 
Hartz mountains of Germany. It is a dark-brown, brittle solid, opaque, and 
possessing a metallic luster somewhat like lead. It closely resembles sulphur 
in its properties, and forms acid compounds with oxygen (selenious and se- 
lenic acids) analogous to sulphurous and sulphuric acids. When heated 
strongly it gives out a powerful odor, like putrid horse-radish, by means of 
which the smallest trace of this element may be detected in minerals, when 
heated before the blow-pipe. 

397. Tellurium, Te,isa rare substance, found chiefly in the mines 
of Hungary and Transylvania ; sometimes native and nearly pure, but gen- 
erally combined with various metals, such as gold, silver, bismuth and cop- 
per. It is a silver- white, brittle solid, possessing a strong metallic luster, 
and by some authorities is classed among the metals. It is, however, closely 
allied to sulphur and selenium in all its properties and combinations. 

Selenium and tellurium both unite with hydrogen to form gaseous com- 
pounds, of singularly offensive and noxious properties. A single bubble of 
seleniuretted hydrogen allowed to escape into a room, produces on those who 



Questions. — "Why do surfaces painted with lead blacken on exposure to this gas? 
Why are zinc paints, for many situations, preferable to lead ? Explain the manner in 
which hydrosulphuric acid is used in chemical analysis. What is said respecting sele- 
nium ? What are its characteristic properties ? What is tellurium ? What are its prop- 
erties ? What i3 said of the compounds of selenium and teUurium with hydrogen ? 
What effect has tellurium upon the animal system f 



PHOSPHORUS. 269 

breatho it, all the usual symptoms of a severe cold and irritation of the 
throat, which continue for several days. But the most singular fact connected 
with tellurium is, " that when certain odorless preparations of this element 
are taken internally, they form compounds within the animal organization 
which impart to the breath and the perspiration so foetid an odor as to render 
the person taking it a kind of horror to every one he approaches ; and this 
lasts sometimes for weeks, though the dose of tellurium administered may not 
oxceed a quarter of a grain." — Johnson. 

SECTION XI. 

PHOSPHORUS. 

Equivalent, 32. Symbol, P. Density, P863. 

398. History.— The credit of the discovery of phosphorus 
is ascribed to Brandt, an alchemist of Hamburg, who 
first recognized it while searching for the philosopher's 
stone in human urine, in the year 1669. Its method of 
preparation was, however, for a long time kept secret. 

399. Natural History and Distribution . — Phosphorus is 
never found in nature in a free state, but exists in small quantities, widely dif- 
fused, in the mineral kingdom, principally in combination with lime. It is a 
constituent of most of the primitive and volcanic rocks, and by the decay of 
these it passes into the soil ; from the soil it is extracted by plants, which 
accumulate it, particularly in their seeds (wheat, corn, oats, etc.). Man 
and animals deriving their support directly or indirectly from plants, in turn 
collect it in their systems — in such quantities that animal products furnish 
almost the only source from which phosphorus is artificially prepared. United 
with oxygen and with lime, it forms the principal mineral constituent of the 
bones. Thus the body of an adult man contains from JL to 12 pounds of 
bones, which contain from 5 to 1 pounds of phosphate of lime (phosphoric 
acid and lime), or from 1 to 2 pounds of pure phosphorus.* " Phosphorus 

* No seed suitable to become food for man and animals can be formed in any plant with- 
out the presence and cooperation of the phosphates, and a field in which phosphate of 
lime, or the alkaline phosphates form no part of the soil, is totally incapable of producing 
grain, peas, or beans. 

Animals which are fed on food which contains no phosphate of lime, gradually lose their . 
nervous irritability, and sink into a state of inanition and torpor, which is speedily followed ' 
by death. A deficiency of phosphate of lime in the food of young children, is also liable to 
produce a disease known as the rickets. As animals derive the phosphate of lime neces- 
sary for their support either directly or indirectly from plants, and as these in turn ex- 
tract it from the soil, it is evident that the fertility of a soil can only be sustained by re- 
storing to it the constituents thus abstracted from it. Hence the value of bones and 
animal products which contain phosphate of lime (as guano) as manures for wheat and 
plants of like character. 

Questions What is the history of phosphorus ? What is said of its distribution in 

nature ? In what condition does it exist most abundantly ? 



270 INORGANIC CHEMISTRY. 

also appears to be essential to the exercise of the higher functions of the 
animal, since it exists as a never-failing ingredient in the substance of which 
the brain and nerves are composed." 

400. Preparation . — Phosphorus was formerly extracted from urine, 
but at the present time it is obtained almost exclusively from bones, from 
which immense quantities are prepared for the manufacture of matches and 
other uses. 

The details of the process of preparation are briefly as follows : — The bones 
are first burned to whiteness and then reduced to a fine powder, which pow- 
der, being a phosphate of lime, insoluble in water, is technically known in 
chemistry and the arts as "bone-ash." So much sulphuric acid and water 
is then added to a suitable quantity of bone-ash as will, in the course of a 
few days, partially decompose it — two thirds of the lime uniting with the 
sulphuric acid to form an insoluble sulphate of lime, while the remaining one 
third continues in combination with the whole of the phosphoric acid to form 
a new compound, which is readily soluble in water. This new compound is 
called superphosphate of lime, and of late years has been extensively intro- 
duced into agriculture, as a ready means of supplying exhausted soils with 
the phosphorus needed for the production of crops. The chemical reaction 
which takes place may be expressed in symbols as follows : — 

Bone-ash. Sulph. acid. Superphosph. lime. Sulph. lime. 

3CaO,P0 5 + 2(S0 3 ,HO) = 2HO,CaO,P0 5 + 2(CaO,S0 3 ) 

The insoluble sulphate of lime and the superphosphate of lime dissolved in 
the acid solution, are then separated from each other by filtration, and the 
latter, evaporated to a syrup, is mixed with charcoal, and heated in an iron, 
or earthen retort. Under these circumstances the charcoal decomposes the 
superphosphate of lime ; — phosphorus rises as a vapor, and passing into cold 
water, is collected and condensed into a solid. The crude phosphorus thus 
obtained is purified by melting under water, and is then east into sticks, in 
which form it is sold. 

401. Properties . — Phosphorus exists in two conditions, viz. : in an 
ordinary state, and in an allotropic state. In its ordinary state it is a soft, semi- 
transparent, almost colorless, waxy-looking solid. It is insoluble in water, 
but readily soluble in ether, alcohol, and in various oils. 

At all temperatures above 32° P., phosphorus, when exposed to the air, 
slowly combines with oxygen, and emits a feeble fight, readily perceptible in 
the dark (hence its name, from <pog , light, and cpepetv, to bear). Exposed to a 
temperature of about 60° F. it bursts into a flame. This extreme combusti- 
bility of phosphorus renders it necessary to keep it continually under water, 
from which it should be taken, for the purpose of experiment, with great cau- 
tion, and be held with a pair of forceps, or upon the point of a knife. TVhen- 

Q0E8TION8. — How is phosphorus obtained ? What is superphosphate of lime ? What 
is the chemical reaction involved in its manufacture ? What are the properties of ordinary 
phosphorus ? What is said of its solubility ? What of its inflammability ? 



PHOSPHORUS. 271 

erer, also, it is desirable to cut it into fragments, the operation should be per- 
formed under water. The burns occasioned by melted phosphorus are 
extremely severe, from the difficulty of extinguishing the flame. 

Phosphorus is also easily ignited by friction, and for this reason is em- 
ployed in the manufacture of matches. It burns in the air with a brilliant 
flame, and in pure oxygen gas with a light so dazzling that the eye can hardly 
sustain it. (§ 282.) 

At a temperature of 111° F., air being excluded, phosphorus melts; and 
when fused under water, it can be molded as readily as wax. At 550° R, 
in close vessels, it boils, giving off a colorless gas. A solution of phosphorus 
in naphtha, by cooling and evaporation, yields crystals of phosphorus. Very 
fine crystals of phosphorus may be also obtained by exposing phosphorus to 
sunlight in a tube either exhausted of air, or filled with a gas which can not 
oxydize it. 

The following experiments illustrate some of the characteristics of this 
element: — 

Place in a glass flask about a quarter of an ounce of ether and a piece of 
phosphorus of the size of a pea. Cork the flask and allow it to stand some 
days, frequently agitating it. In this way an ethereal solution of phosphorus 
will be obtained, which, when rubbed upon the hands, renders them luminous 
in the dark. The explanation of this phenomenon is, that the ether evapo- 
rates, and leaves the phosphorus which it held in solution upon the hands in 
a state of minute subdivision. In this condition it combines with the oxygen 
of the air, or undergoes a slow combustion, diffusing a white smoke and a 
pale greenish light. Heat is at the same time evolved, but not sufficient to 
occasion ignition. By rubbing the hands, the light is rendered more vivid, 
as a fresh surface of phosphorus is thus continually presented to the oxygen 
of the air. 

If we moisten a lump of white sugar with an ethereal solution of phos- 
phorus, and throw it into hot water, the heat of the water will volatilize both 
the ether and the phosphorus ; and the vapors, in rising to the surface of the 
water, and coming in contact with the oxygen of the air, will inflame spon- 
taneously. 

If we pour an ethereal solution of phosphorus upon fine blotting-paper, the 
latter will ignite spontaneously after the ether has evaporated. 

If we place a piece of phosphorus of the size of a pea upon blotting-paper, 
and sprinkle over it some soot or finely-pulverized charcoal, the phosphorus, 
after a little time, melts, and at length spontaneously inflames. The finely- 
pulverized charcoal causes this combustion, owing to its porosity, which en- 
ables it to readily absorb oxygen from the air. This oxygen is in turn im- 
parted to the phosphorus, and by uniting with it, occasions heat, which, 
prevented by the non-conducting properties of the charcoal from escaping, 
accumulates, and occasions combustion. 

Questions. — What property renders phosphorus available for the manufacture of 
matches ? What experiments illustrate the characteristics of phosphorus ? 



272 INORGANIC CHEMISTRY. 

Phosphorus when taken internally is a most violent poison, and in combin- 
ation with other substances, is frequently used for the destruction of rats and 
vermin. The so-called rat-exterminating poison is composed of 1 dram of 
phosphorus, 8 ounces of hot water, and 8 ounces of flour. 

402. Allot ropic or Amorphous Phosphorus . — It has long 
been noticed, when phosphorus is exposed to the action of light for a consid- 
erable length of time, that its exterior becomes coated with a red powder, and 
that the same product is formed when phosphorus is burned with a limited 
supply of air. This red powder was always supposed to be an oxyd of phos- 
phorus, but within a recent period, Prof Schrotter of Vienna has succeeded 
in demonstrating that the substance in question is merely an ailotropic stato 
of ordinary phosphorus. He has shown that if ordinary phosphorus be sub- 
mitted to the action of a prolonged heat, within certain limits, and under 
circumstances involving an entire exclusion of oxygen, it becomes converted 
into a brick-red substance; — "not soluble in any of the ordinary solvents of 
phosphorus — not igniting by ordinary friction — not luminous at ordinary tem- 
peratures — not poisonous; distinguished, in fact, for negative properties, as 
common phosphorus is for active ones ; and yet this wonderful change is only 
molecular ; that is, the phosphorus is not converted into a compound : it has 
combined with nothing, it has lost nothing, but its particles have probably 
arranged themselves with respect to each other, in a manner different from 
that of the particles of common phosphorus." Common phosphorus we aro 
obliged to keep in water, for the purpose of guarding against spontaneous 
combustion ; ailotropic phosphorus, however, may be kept unchanged in at- 
mospheric air, and may be handled or even carried in the pocket with im- 
punity. Exposed to a temperature of about 480° P., it melts, and returns to 
the condition of ordinary phosphorus ; and at a temperature of 500° it bursts 
into flame with a sort of explosion. The identity of the two substances is 
proved by their ready conversion into each other, and by the fact that the 
compounds which they form with other bodies are the same. 

403. Matches . — Some notice of the history and manufacture of matches 
is appropriate in connection with the subject of phosphorus. 

The comparatively low temperature at which sulphur ignites, early sug- 
gested its application to the end of a strip of dry wood, as a means of procur- 
ing flame. The old sulphur match was chiefly used in connection with a fl'.nt 
and steel, and a box for holding tinder. The tinder, formed by the partial 
combustion of a linen or cotton rag, was first ignited by means of a spark 
resulting from a collision of a flint and steel, and this in turn communicated 
the fire to the match. Fifty years ago, a " tinder-box" was as much an indis- 
pensable article of household economy as a paper of matches is at the present 
day. 

Soon after the discovery of phosphorus, attempts were made to use it as a 

Questions. — What is said of the poisonous properties of phosphorus ? What is rat- 
poison ? What is said of ailotropic phosphorus ? In -what respects does ailotropic differ 
from ordinary phosphorus ? How can we prove that ailotropic and common phosphorus 
are the same ? What is said of the history and origin of matches ? 



PHOSPHORUS. 273 

method of procuring fire, but its costliness prevented its general introduction 
and use for this purpose, for nearly one hundred and fifty years. One of the 
first methods of applying it was to put a piece of phosphorus in a phial, and 
then to stir it with a hot iron wire ; the phosphorus was partially burnt in the 
confined portion of air, and the interior of the bottle became covered with an 
oxyd of phosphorus; on removing the wire, the phial was corked tightly for 
use. When a light was wanted, a common sulphur match was dipped into 
the bottle, and a small portion of the phosphorus adhering to the tip, flame 
was produced by the energetic chemical action of the sulphur and the phos- 
phorus. Various other inventions were employed for procuring fire ; — such 
as the sudden condensing of air in a syringe furnished with a piston and an 
arrangement for holding tinder — apparatus for igniting tinder by an electria 
spark — Dobereiner's Lamp (§ 297), etc., etc. In fact, during the whole of the. 
last century, and even later, the invention of a safe, convenient, and reliably 
agent for kindling a fire or light, was regarded as one of the great wants of 
the age. 

The next important step taken in perfecting the match, was the employ- 
ment of chlorate of potash. The match stick was tipped with a mixture 
of chlorate of potash and sugar, and ignited by immersion in a litcle bot- 
tle containing asbestos soaked in_ sulphurki_acid. (For explanation of thia 
phenomenon see § 368.) Matches thus prepared were put up incases, which 
contained in one compartment a small bottle of acid. Their price, when first 
introduced, was $4 75 for a case of 100; but subsequently was reduced to 
50 cents. These matches continued in use until within a very recent period. 

The next important invention was that of the so-called " Lucifer Matches," 
which were tipped with a paste of chlorate of potash and~sulpliuret of- anti- 
mony mixed with starch, and were ignited by drawing the match between 
two surfaces of sand-paper-. These were the first friction matches. In 1834, 
phosphorus was substituted in the place of antimony, and the match was ig- 
nited by friction upon any rough surface. Subsequently, saltpeter was sub- 
stituted in the place of chlorate of potash, which produced quietlgnition in- 
stead of detonation. 

The details of the manufacture of matches at the present time are generally 
as follows : The ends of the wooden match-splints, which are sawed by ma- 
chinery, are first sulphured, by immersion in a pot of melted sulphur. "When 
dried, they are next dipped in the phosphorus composition, which is a paste 
prepared by mixing together in a hot solution of glue, or gum, in water, phos- 
phorus, saltpeter, and generally red-lead and some coloring ingredients ; — if 
the tips of the matches are to be red, vermillion is added ; or if blue, Prus- 
sian blue. 

The various reactions which take place when a match is fired are as follows : 
the phosphorus contained in the composition is first ignited by the heat 

Questions. — What were some of the early methods resorted to for the purpose of ob- 
taining a light? When was phosphorus first applied to the manufacture of matches? 
What were the first friction matches ? How are matches manufactured ? What chem- 
ical reactions are involved in the firing of a match ? 

12* 



274 INORGANIC CHEMISTRY. 

evolved by friction or compression; and the heat occasioned by its combustion 
decomposes the saltpeter and the red-lead; these substances, in their decom- 
position, evolve oxygen, which supports the flame, adds to its heat, and en- 
ables it to ignite the sulphur, which in turn inflames the wood. The odor of 
a burning match is occasioned by the combustion of the sulphur, and in some 
recent inventions, has been obviated by the substitution of stearine in the 
place of sulphur. The temperature required for kindling matches varies from 
150 to 160° F* 

The manufacture of matches is attended with danger, not only from the 
highly inflammable nature of the ingredients used, but also from the fact, that 
a continued exposure to the vapor of phosphorus, produces a disorganization 
of the jaw-bones, causing excruciating suffering, and usually terminating in 
death. The phosphorus, in the first instance, attacks a little spot of decay 
upon a tooth, and from this ulceration spreads with great rapidity. Of these 
evils the first is greatly lessened, and the second altogether avoided, by the 
use of the amorphous or allotropic phosphorus, before described. 

404. Compounds of Phosphorus with x y g e n • — Phos- 
phorus unites with oxygen to form four compounds, viz. : — 

Composed by weight of 

Phosphoric acid POs 32 phosphorus 40 oxygen. 

Phosphorous acid PO3 32 " 24 " 

Hypophosphorous acid PO 32 " 8 " 

Oxyd of Phosphorus P2O 64 " 8 " 

405. Phosphoric Acid, PO 5 . — This acid, which is the 
most important of the oxyds of phosphorus, is the sole 
product of the rapid combustion of phosphorus in oxygen, 
or atmospheric air. 

It appears as a dense white vapor, which condenses on cooling into a white 
powder. It may be easily collected by burning phosphorus in air under a 
dry bell glass. As thus prepared, it has so great an avidity for water, that 
when brought in contact with it, it hisses like a hot iron. Exposed to the 
air for a few moments, it absorbs moisture, and deliquesces to a liquid. "When 
once converted into a hydrate, water can not be entirely separated from it. 
Its solution is intensely acid, and when evaporated to dryness, yields, on cool- 
ing, a glassy, transparent solid, known as glacial phosphoric acid. 

Phosphoric acid may also be prepared by the action of nitric acid on phos- 
phorus, and also from bones, by the action of sulphuric acid. It combines 

* Some idea of the importance of the manufacture of matches as a branch of industrial 
art, may be formed from the following statistics of materials consumed in Austria in one 
year, 1849, for this purpose— 125,090 lbs. of saltpeter, 32,500 lbs. of phosphorus, 1,500,000 
lbs. of sulphur. 

Questions. — What is the temperature required for kindling a match ? What effect has 
the vapor of phosphorus upon the animal system ? What compounds does phosphorus 
form with oxygen ? How is phosphoric acid prepared ? What are its properties ? 



PHOSPHORUS 



275 



with water in three proportions, to form three distinct hydrates, which unite 

with bases to form three classes of salts. The nomenclature and composition 

of these hydrates, which are of great scientific interest, may be represented as 

foUows: — , ., 

Acids. 

Monobasic or metaphosphoric acid HO.POs, 

Bibasic or pyrophosphoric acid 2HO.PO5, 

Tribasic or common phosphoric acid 3HO.PO5. 

It is in the form of phosphoric acid, united with some base, generally lime 

or magnesia, that phosphorus exists in the bones, in the seeds and tissues of 

plants, and in the soil. 

406. Phosphorus A c i d > P0 3 is the principal product which results 
from the slow combustion which occurs when phosphorus is exposed to the 
oxygen of the atmosphere. It may also be formed by burning phosphorua 
with a limited supply of air. 

The other oxyds of phosphorus are comparatively unimportant. 

407. Phosphorus and Hydrogen , — P hosphuretted Hy- 
drogen, P H 3 . — Phosphorus unites with hydrogen in three proportions to 
form three compounds; one of which, a gas, phosphuretted hydrogen, pos- 
sesses the property, under certain circumstances, of inflaming spontaneously 
on exposure to air, or oxygen gas. 

This substance is conveniently prepared by heating fragments of phosphorus in 
a retort, with a strong solution of caustic potash, or cream of lime, prepared from 
lime recently slacked.* On the "PiQ. 132. 

application of a gentle heat to 
the retort, the beak of which is 
caused to dip slightly beneath 
the surface of water, the gas is 
evolved, and the bubbles, as 
they rise and come in contact 
with the air, spontaneously in- 
flame. (See Fig. 132.) Each 
bubble, as it breaks and ignites, 

Pig. 133. produces a beautiful white wreath of smoke (vapor 

^-^TTjVK (V/^£^n of phosphoric acid), composed of a number of concen- 

/^\V W^v'VHsV^^ trie rings, revolving around the axis of the wreath, as 

^(^^^^T^5>^ [t ascends ( see Fi g- 133 ); thus tracing before the eye, 

^*>XA.ysS-J/ with perfect distinctness, the peculiar gyratory move- 

* In this experiment it is best to employ a very small flask or retort, and in order to 
avoid the presence of atmospheric air, it is advisable to fill it full to the neck with the 
cream of lime, or potash solution. For an ounce flask, a piece of phosphorus of the size 
of a pea is sufficient. It is best, also, not to apply heat to the glass directly, but to place 
it in a basin containing a solution of salt, which is then heated to a boiling temperature 
by a spirit lamp. 

Questions. — "What is said of its combinations with water ? In what state does phosphorus 
generally exist in nature ? What is said of phosphorus acid ? "What is said of phosphuret- 
ted hydrogen ? How is it prepared ? "What phenomenon attends its evolution in air ? 





276 INORGANIC CHEMISTRY. 

ments imparted to air by the impulse of a force acting 
suddenly upon a mass of air in all directions, from a 
center. The same phenomenon is also seen in the rays of 
smoke produced by the mouth of a skillful tobacco- 
smoker, and frequently also, upon a much larger scale, 
during the discharge of cannon on a still day. 

Phosphuretted hydrogen may be more simply pre- 
pared by throwing into a glass of water a few pieces of 
phosphuret of calcium. This suV stance, by contact with 
the water, is decomposed, and evolves the spontaneously 
inflammable gas. (See Fig. 134.) 

408. Properties . — Phosphuretted hydrogen is p. 
colorless, transparent gas, possessing an offensive, foetid odor, and producing 
a poisonous action upon the s} r stem, when inhaled. It loses its spontaneous 
inflammability by standing for a time over water, and also by the addition of 
the vapor of some inflammable bodies, such as ether, oil of turpentine, etc. By 
varying the conditions of its preparation, it may also be evolved without the 
self-lighting power. 

The production of this gas, by the decay of bones and other organic pro- 
ducts in wet, swampy places, and its subsequent ignition in contact with the 
air, is supposed to have originated fhe popular superstition known as the 
"Ignis Patuus," or "Will-o'-the-wisp."* 

SECTION XII. 

BORON. 

Equivalent, 10*9. Symbol, B. 

409. History and Distribution. — Boron is an element 
that is always found in nature in composition with oxygen, 
forming boracic acid. The latter substance is found only 
in few localities, and in comparatively small quantities. 
United with soda it forms a salt, borax, which is a well- 
known article of commerce. 

Until within a very recent period (1856-1), comparatively little has been 
known respecting the nature of the pure element, boron. It has been recently 
ascertained, however, that it is closely allied to carbon, and that it exists in 

* It is generally taken for granted that luminous appearances in the air are often seen 
in the vicinity of swamps, grave-yards, or other receptacles of decaying organic matter. 
Such, however, is not the fact ; and it is extremely doubtful whether any well authenti- 
cated instance of such an appearance can he cited. The generally-received account of the 
" Ignis fatuus" must therefore he regarded as a fiction. 

Questions. — What are the properties of phosphuretted hydrogen ? What popular su- 
perstition is it supposed to have originated ? What is said of boron ? 



BORON 



277 



three allotropic conditions, viz., as a chocolate-brown amorphous substance ; 
as an opaque, semi crystalline body, occurring in thin plates, with a black- 
lead luster ; and, lastly, in a crystalline condition, resembling the diamond in 
luster, hardness, and refractive power. As yet, chemists have been only able 
to obtain it in very minute crystals ; but if larger crystals can be prepared, it 
will undoubtedly take rank as one of the most valuable of gems. Its method 
of preparation consists essentially in fusing boracic acid with the metal alum- 
inum. 

410. Boracic Acid, B0 3 is found in small quantities in Thibet and 
in South America, but the principal supply is from volcanic districts of Tus- 
cany, in Italy, called lagoons, where jets of vapor and of boiling water, charged 
with boracic acid, are continually issuing from fissures in the earth.* 

The manner in which the boracic acid is collected is as follows : A locality 
is chosen, where the soil is observed to possess a high temperature, and a 
basin of moderate depth (A, Fig. 135) is excavated, and walled up with 

Fig. 135. 




a masonry — openings, v, being left in the bottom for the admission of the 
steam escaping from the earth, f "Water from adjacent springs is then con- 
ducted into the basin, which absorbs the boracic acid brought up by the as- 
cending vapor, and at the same time becomes heated to the boiling tempera- 
ture. After the lapse of twenty-four hours, the solution is drawn off into a 
similar- constructed basin, B, at a lower level, from thence into a third, C, and 



* " As you approach the lagoons, the earth seems to pour out boiling water, as if from 
volcanoes of various sizes, in a variety of soils, but chiefly of chalk and sand. The heat 
in the immediate neighborhood is intolerable, and you are drenched with vapor, which 
impregnates the atmosphere with a strong and somewhat sulphurous smell. The whole 
scene is one of terrible violence and confusion : — the noisy outbreak of the boiling water ; 
the rugged and blasted surface ; the volumes of vapor ; the impregnated atmosphere. 
The ground burns and shakes beneath your feet, and the whole surface is covered with 
beautiful crystallizations of sulphur and other minerals." — Db. Bowsing. 

t The dimensions of these basins vary from 100 feet in circumference and 7 feet deep, 
to 500 and 1000 feet in circumference and 15 to 20 feet deep. 



Questions. — What are its properties ? What is said of boracio acid ? How is it col, 
lected ? 



278 INORGANIC CHEMISTRY. 

so on, until the water, having absorbed the greatest possible amount of bor- 
acic acid, is transferred into shallow tanks, E, for purification. The solution 
thus obtained is evaporated in leaden pans heated by the volcanic steam, 
until the boracic acid contained in it is deposited in white, scaley crystals. 
The annual production of boracic acid from these sources is at present about 
three million pounds. 

Boracic acid has a white, pearly luster and a greasy feeling. It is a feeble 
acid, sparingly soluble in cold water, but dissolving in three times its weight 
of boiling water. Its solution in alcohol burns with a beautiful green flame, 
which constitutes a test of the presence of boron. This property may be 
illustrated by igniting a solution of borax in alcohol in a shallow cup, and 
stirring the liquid with a glass rod while burning. 

411. Borax, or Biborate of Soda, is formed by adding car- 
bonate of soda to a solution of boracic acid. This salt is composed of two 
equivalents of acid, one of base, and ten of water — its constitution being rep- 
resented as follows, NaO, 2BO-f-10 HO. Borax is obtained naturally in 
small quantities and in an Impure state, by the evaporation of the waters of 
certain lakes in Thibet, and is exported under the name of tincal. 

Borax is chiefly used in the arts as a flux in the welding, soldering, and 
refining of metals. 

The term flux is applied in metallurgy to those sub- 
stances which assist fusion, either by expediting the pro- 
cess, or by protecting the substance melted from oxyda- 
tion. 

Borax, when heated, bubbles up, loses its water of crystallization, and at a 
temperature below red-heat, melts into a transparent glass. The property 
which this glass possesses of dissolving the metallic oxyds, gives to borax its 
value as a flux. Eor example : in the welding of iron, a union between two 
surfaces can not be effected unless both are clean and perfectly free from ox- 
ydation ; but a piece of iron can not be strongly heated without the formation 
of a layer of oxyd upon its surface. This difficulty is obviated by sprinkling 
the hot surfaces with powdered borax, which, as it melts, not only dissolves 
off the oxyd, or scale already present, but keeps the metal bright by prevent- 
ing all further oxydation. 

Borax is also much used as a test before the blow-pipe, for recognizing the 
presence of certain metallic oxyds. For this purpose, a small crystal of borax 
is fused upon the end of a bent platinum wire, and a minute quantity of tho 
substance to be tested is melted with the salt in the flame of the blow-pipa 
The peculiar color which the borax glass receives, indicates the character of 
the coloring substance : thus, with an oxyd of chromium, the borax forms an 
emerald-green glass ; with oxyd of cobalt, a blue ; with manganese, a violet ; 
with iron, a yellow, and so on. 

QuKSTfONg. —What are the properties of boracic acid ? "What is borax ? For what pur- 
pose is it used in the arts? What is a flax? What gives to borax its value aa a flux! 
Illustrate this. How does borax serve as a blow-pipe reagent? 



SILICON. 



279 



SECTION XIII. 

\ SILICON, or SILICIUM. 

Equivalent, 21 -2. Symbol, Si. 

412. Distribution. — Silicon, in combination with oxy- 
gen, is the most abundant of all the solid substances 
which compose the crust of our globe. All rocks which 
are not calcareous (lime) are silicious. 

It is only within a very recent period (1855-*7) that chemists have been en- 
abled to obtain any very definite knowledge respecting the nature and prop- 
erties of pure silicon. It is now known to exist, like carbon and boron, in 
three allotropic conditions ; in an amorphous nut-brown powder ; in a condi- 
tion resembling graphite (black-lead) ; and in a crystalline condition. It has 
most of the characteristics of the metals, and by the most recent authorities is 
classed with them. As prepared by a somewhat complicated process, it is 
easily fusible, and may be run into ingots and alloyed with copper and iron. 
At a meeting of the French Academy in 1857, two small cannon composed 
of an alloy of copper and silicon were exhibited. 

413. Silicic Acid, or Silica, SiOs, is the principal oxyd 
of silicon, and the most important of all its compounds. 
In fact, it is in this condition only that silicon is found in 
nature. 

"When pure, or merely colored by small quantities of different oxyds, it is 
very generally termed quartz. It is frequently found crystallized, its ordinary 
form being a six-sided prism, terminated by six-sided pyra- Fig. 136. 
mids, as in rock-crystal. (See Fig. 136.) Sometimes the 
prism is very short and disappears entirely, and the pyramid 
only is seen, as in common quartz. In transparent and col- 
orless rock-crystal, silica is almost absolutely pure, and in this 
condition is not unfrequently used in jewelry. Amethyst is 
crystallized quartz, colored purple by the presence of protoxyd 
of manganese. Common flint, agate, carnelian, chalcedony, 
jasper, and opal, are other varieties of nearly pure silica, 
their colors being occasioned by the presence of different me- 
tallic oxyds. Common sand is mainly composed of silica, 
colored yellow or brown by the presence of oxyd of iron ; sand cemented into 
rock-masses, through the agency mainly of silica, is termed " sandstone." 

Many plants absorb silica from the soil in considerable quantity, and deposit 

Qtjestions. — What is the natural history of silicon ? What is known respecting th« 
pure element? What is silica ? What is quartz? In -what minerals does silica nearly 
pure exist ? What is amethyst ? To what are the colors of agate, chalcedony, opal, etc., 
due ? What is common sand ? What is sandstone ? Does silica exist in plants? 





280 INORGANIC CHEMISTRY. 

it upon the exterior of their stalks, or stems. Examples of this may be seen 
in the glossy coating which invests the outside of straw, cane, rattan, bam- 
boo, etc. In these instances, the silica subserves the same purpose in the 
structure of the plant that bones do in the structure of men and animals — 
that is, it gives to the stalk firmness and stiffness. The straw of wheat grown 
upon soils deficient in " soluble silica," is so weak as to be hardly capable 
of supporting the weight of the seed. 

In the animal kingdom, silica exists in the feathers and hair of animals, 
and recent researches have also detected it in the blood. 

414. Properties . — Pure silica is not affected by the heat of the strong- 
est wind furnace, but before the flame of the oxyhydrogen blow-pipe it melts 
into a transparent glass. In its native state it is insoluble in pure water, and 
in all acids except hydrofluoric. In hardness it approaches the precious gems, 
and it scratches glass easily. 

Silica, although it presents the characters of an earth, is in reality an acid, 
and a most powerful one. Under all ordinary circumstances, however, its 
acid properties are not manifested by reason of its almost entire insolubility. 

When silica is digested in solutions of the alkalies it gradually unites with 
them, and forms salts — silicates of potash or soda — which are readily soluble. 
Even flints in their unground condition, or fragments of quartz when placed 
in strong solutions of caustic potash or soda, at a high temperature, are readily 
caused to pass into solution. "When solutions of silica in an excess of alkali 
are concentrated, a semi-fluid mass closely resembling a solution of starch is 
produced. This product is known as soluble glass, and is readily soluble in hot 
water, and can be applied as a varnish for rendering surfaces of wood or cloth 
fire-proof. It has also been used to some extent as a substitute for starch or 
gum in the stiffening of fibrous substances. Ancient monuments or buildings 
constructed of soft and friable stone may bo preserved in a great measure from 
decay and the action of the weather by a coating of soluble glass. For prac- 
tical purposes, soluble glass is formed by fusing together 8 parts of carbonate 
of soda (or 10 of carbonate of potash) with 15 parts of pure sand, and 1 of 
charcoal. The product, when pure, resembles ordinary glass, but dissolves 
in boiling water without residue. 

When a solution of soluble glass is rendered acid by the addition of hydro- 
chloric acid, the silica after a little time separates as a transparent, tremu- 
lous jelly. This is a hydrate of silica, which once precipitated in this manner, 
is no longer soluble in either water or acids. By preventing the escape of 
moisture, it may be preserved in a gelatinous condition ; but if once allowed 
to dry, it forms a white, gritty powder — white silicious sand. 

Most natural waters contain a little soluble silica, which can be only separ- 
ated by evaporating the water to dryness. Waters which contain alkaline 



Questions.— What are illustrations? What is said of silica in the animal kingdom? 
What are the properties of silica? Is silica an acid? Under what circumstances does ifc 
pass into solution? What is soluble glass? What are its properties and uses? How- 
may silica be separated from its solution in alkalies? Does silica exist in natural waters ? 



SILICON. 



281 



carbonates dissolve it more freely, and when the action of the alkaline liquid 
is aided by that of a high temperature, as is the case with the Geysers, or hot 
springs of Iceland, very large quantities of silica are dissolved. As the liquid 
cools, the silica is deposited, in an insoluble form, on the surrounding objects 
in contact with the waters, forming "petrifactions." Agates, chalcedony, 
camelian, and onyx, have undoubtedly been thus formed by the slow deposi- 
tion of silica from its solution in' water. 

The acid character of silica is especially exhibited when it is exposed, in 
contact with other salts, to a high temperature. It then displaces the most 
powerful acids from their combinations, and uniting with their bases, forms 
silicates. Thus when carbonate or sulphate of potash, soda, or lime, are mixed 
with silica and fused, the silicic acid displaces the carbonic and sulphuric 
acids from their combinations, and forms silicates of potash, soda, or lime. All 
the forms of clay r feldspar, mica, hornblende, and a great number of our most 
common minerals, are the salts of silicic acid.* 

415. Fluoride of Silicon, SiFI. — Fluosilicic Acid. — In order 
to prepare this gas, equal parts of finely-powdered fluor-spar and silicious 
sand, or powdered glass, are mixed in a 
capacious flask, with six parts of concen- 
trated sulphuric acid. On the application of 
heat, hydrofluoric acid is liberated, and this 
immediately attacking the silica, produces a 
colorless gas, of which silicon is a constitu- 
ent. "When passed into water, the gas 
is decomposed, silicon is precipitated in the 
form of gelatinous silica, and the water 
becomes a solution of hydrofluosilicic acid. 
This reaction, which constitutes a very inter- 
esting experiment, may be easily exhibited 
by an arrangement of apparatus as repre- 
sented in Fig. 137. 

In transmitting the gas into water, the ex- 
tremity of the evolution tube should not be 
brought into direct contact with the water, 
lest it become at once obstructed by the de- 
posited silica ; but it should be plunged |Bgl 
beneath the surface of a little mercury contained in the bottom of the receiv- 



FiG. 137. 




* The composition of many of the silicious minerals is extremely complex, and in a 
scientific point of view, extremely interesting. Upon one group alone, the zeolites — hy- 
drated silicates of alumina, with lime, potash and soda — an immense amount of labor haa 
been expended by many of the most eminent chemists of the present century, and yet their 
chemical formula and most natural relations are still open to question. 



Questions. — Explain the circumstances. What is the supposed origin of agates, car- 
nelians, etc. ? "When is the acid character of silica especially manifested ? Illustrate. 
What are examples of natural silicates? What is said of fluosilicic acid? What occurg 
when this gas is passed into water ? 

23* 



282 INORGANIC CHEMISTRY. 

ing vessel, as is represented in Fig. 137. As the gas ascends through the mer- 
cury, and enters the water, it exhibits a most curious phenomenon ; each bub- 
ble becoming invested with a white bag of silica > and rising, like a miniature 
balloon, to the surface ; it often happens, also, in the course of the experiment, 
that the gas forms tubes, or conduit pipes of silica in the water, through 
which it gains the surface without decomposition. 



SECTION XIV. .' 

CARBON. 

Equivalent, G. Symbol, C. Specific gravity as diamond, 3*3 to 3 '5. 

416. History. — Carbon is one of the most abundant and 
important of the elementary bodies. In the inorganic 
kingdom of nature it exists chiefly as mineral coal ; in the 
state of carbonic acid diffused throughout the atmosphere ; 
and as a constituent of the great rock masses — carbonates 
of lime and magnesia. In the organic kingdom, it is the 
characteristic ingredient of all substances which are pro- 
duced directly or indirectly from animal or vegetable or- 
ganisms. 

Carbon is found pure in nature in three allotropic forms 
or conditions, each of which, although possessed of identi- 
cally the same chemical composition, exhibits properties 
singularly different from the others, and peculiar to itself. 
These are, 1. The Diamond ; 2. Graphite, or Plumbago ; 
3. Mineral Coal and Charcoal. 

417. The Diamond is pure carbon, crystallized. 

It is found throughout a wide extent of country in India, but chiefly at 
Golconda, and in certain districts of Borneo and Brazil. It has also been 
found associated with gold and platinum in the Ural mountains, and in a few 
instances in the United States, principally in the gold districts of North Car- 
olina.* In only a few instances has the diamond ever been found imbedded 
in rock masses, but it is usually associated with materials transported by 
water from a distance, such as loose sand and rolled graveL In their natural 



* The largest diamonds come from Golconda, but Brazil furnishes the greatest quan- 
tity. The yearly produce of the Brazilian mines at the present time is estimated at from 
10 to 13 lbs., a large proportion of which, however, are unfit for jewelry. 

Questions. — What is said of the distribution of carbon in the two great kingdoms of 
nature ? In what conditions is carbon found pure naturally ? What is the diamond ? 
Under what circumstances is it found in nature ? 



CARBON 



283 



condition, diamonds have usually the appearance of semi-transparent, rounded 
pebbles, and are covered by a thin, opaque crust ; on removing this crust, 
their exceeding brilliancy becomes apparent. 

The diamond is generally colorless, and such specimens possess the great- 
est value ; but it is not unfrequently found of a blue, yellow, -pm 138 
or rose color, and sometimes green or black. 

The primitive form of the diamond is that of an octohedron 
(see Fig. 138), but its faces are often convex, and its edges 
rounded. It is cut for jewelry in three forms, known as bril- 
liants, Fig. 139, roses, Figs. 140, 141, and tables, Figs. 142, 143.* 




Fig. 139. 



Fig. 140. 



Fig. 141. 



Fig. 142. 



Fig, 1 4<1. 




The diamond is the hardest of all known substances, and can be only cut 
or abraded by means of its own powder — inferior and imperfect stones being 
broken down for this purpose. The process of cutting is effected by a hori- 
zontal disc of steel, covered with diamond dust and oil, and revolving with a 
velocity of two or three thousand times per minute. The gem is fixed in a 
mass of lead, which is fitted to an arm, one end of which rests upon a 
table over which the plate revolves, while the other, sustaining the diamond, 
is pressed upon the plate by movable weights, at the discretion of the ope- 
rator. The gem, however, cannot be ground into any form at pleasure, but 
only in directions parallel to its lines of cleavage. (§ T3.)f 



* The f jrm of the brilliant shows the gem to the best advantage, and may be recognized 
by its flat summit ; the surface of a rose diamond is covered with equilateral triangles, 
terminating in a sharp point. The table form is only given to plates, laminae, or slabs of 
diamonds, which have a small depth compared to their superficial extent. The brilliant 
and the rose lose in cutting and polishing somewhat less than half their weight, so that 
the value of a cut stone is double that of an uncut one, without reckoning the expense of 
the process. 

t The method of cutting diamonds was discovered in 1455, and is still unknown in its 
perfection among Eastern nations. The business in Europe is carried on almost exclu- 
sively in Amsterdam, Holland. The heat developed in the cutting is frequently so great 
as to melt the lead in which the diamond is imbedded, and the time occupied in cutting a 
single face varies from 3 to 30 hours. 

The weight of diamonds is estimated in carats — 150 of which are equal to 1 ounce Troy, 
or 4S0 grains. " The rule for estimating the value of diamonds is peculiar, and supposing 
the gems under comparison to be equal in quality, may be expressed as being in the ratio 
ef the squares of their respective weights. Thus, supposing three diamonds to exist, 
weighing respectively 1, 2, and 3 carats ; their respective values would be as one, four, 
and nine. This rule, however, can only be considered as applying to gems of a moder- 
ate size ; as very large diamonds, if estimated according to this mode of calculation, 
would become expensive beyond the means of the richest to command." 



Questions. — What is its primitive form ? In what three forms is it cut for jewelry ? 
What is said of its hardness ? How is it cut ? 



284 INORGANIC CHEMISTRY. 

Tho diamond is remarkably indestructible, and is not acted upon by any 
solvent, neither is it affected by heat alone — since it may be heated, when 
removed fiom the access of air, to a white heat without injury. In the open 
air it burns at about tho melting point of silver, and 'is converted into coal, 
or carbonic acid gas. 

Many attempts have been made to fuse or crystallize some pure form of 
carbon, or, in other words, to manufacture diamonds, but they have all failed. 
In 1853, M. Despretz of Paris succeeded, after long-continued voltaic action, 
in depositing at one of the terminal poles of a galvanic battery a quantity of 
carbon in the form of minute microscropic grains ; these grains appeared to bo 
octohedral crystals, and were capable of cutting and polishing diamonds and 
rubies ; hence it has been inferred that they were actually themselves dia- 
monds. 

The origin of the diamond has been a subject of much curious speculation, 
inasmuch as the circumstances under which it is found in nature afford us 
no clue to tho process of its formation. Tho structure of the diamond itself, 
however, furnishes us with some positive information on the subject, and in- 
dicates that it is a product, either directly or indirectly, of the vegetable king- 
dom.* Sir David Brewster, who has given much attention to the subject, 
is inclined to the opinion, that the diamond is a drop of fossilized gum, anal- 
ogous in some respects to amber. 

418. The largest known diamond is an uncut gem belonging to the 
crown jewels of Portugal. It was found in Brazil about the year 1808, and 
weighs 1,680 carats, or about 11 ounces. About the middle of the 16th 
century a diamond was found at G-olconda in India, which had the form of 
half a hen's egg, and weighed nearly 6 ounces. This diamond, which was 
long known as tho Great Mogul from its possessor, has disappeared, and is 
supposed to have been broken up ; — the separate pieces, according to this 
theory, now constituting three of the largest existing diamonds, viz., 1, the 
great diamond in the possession of Russia., weighing 196 carats : 2d, the 
Koh-i-noor, in the possession of the Queen of England, which weighed before 
cutting 186 carats, and after cutting 103 carats; and 3d, a diamond belonging 
to the Shah of Persia, of the weight of 130 carats. The value of the Russian 
diamond has been estimated at 20 millions of dollars, and that of the Koh- 
i-noor at from 3 to 10 millions. 

The other large diamonds most worthy of notice are the following : — A 
yellow diamond belonging to the crown of Austria, which weighs 139 carats. 
The size and form of this diamond, which was onco sold as a bit of colored 



* The evidence on this point is principally as follows ; diamonds have been found in- 
closing vegetable matter, and when the diamond is burned a minute yellowish ash is left, 
which generally possesses a cellular structure. Some other proof is also afforded by tho 
action of refracted and polarized light. 

Questions. — What is said of its indestructibility? Ilavo any attempts been made to 
manufacture diamonds ? What is said of the origin of the diamond ? What evidenca 
have we on the subject ? How large a diamond has ever been found ? What are soma 
of the most valuable diamonds ? 



CARBON 



285 



Fig. 144. 





Fig. 146. 



, are represent- 
ed in Fig. 144. The 
Pitt or Regent dia- 
mond belonging to 
France, is repre- 
sented in Fig. 145. 
the dotted line be- 
ing the outline of 
the stone before cut- 
ting. This diamond, 

which is a light blue color, i3 allowed to be the ~ — 

finest in existence, and weighs 131 carats. It was brought from India by a 
Mr. Pitt, and sold to the Regent of France in 1T17 for aboat $700,000. Its 
value, as estimated by a commission of Parisian jewelers, is about $3,000,000. 
Fig. 146 represents a very beautiful diamond known 
as the Pigott diamond, which weighed 4*7 carats, 
and was sold for about $120,000.* 

419. Graphite, or Plumbago, is the 
secoDd allotropic form in which car- 
bon occurs uncombined in nature. It 
has a metallic, leaden-gray luster, feels unctuous to the 
touch, and is generally known as " black-lead/' although 
it has no trace oflead in its composition. 

It is found chiefly in the older rocks (in many localities in the United 
States), chiefly in beds or rounded masses, but sometimes crystallized in flat 
six-sided prisms. It is never found perfectly pure, but usually contains a 
little iron and some other accidental impurities. Like the diamond, it can not 
be fused or volatilized by the action of the most intense heat ; it burns, how- 
ever, in oxygen gas, forming carbonic acid. 

The principal use to which plumbago is practically applied is for the manu- 
facture of " lead pencils." Most of the ordinary pencils now used are manu- 
factured from a factitious paste, made of powdered plumbago, antimony, and 
Ejulphur fused together, and cast into blocks. These blocks are then sawed 
into small rectangular prisms, which are subsequently inclosed in cylinders of 
cedar wood. The best drawing-pencils are, however, made, by reducing the 
plumbago to a fine powder, freeing it from impurities, and then subjecting it 
to enormous hydrostatic pressure, simultaneously with the abstraction of all 
remaining traces of air by means of an air-pump. A coherent block is thus 




* This diamond is not in existence, but was destroyed by a Turkish pasha in order to 
prevent it from falling into the hands of his enemies. 

So rare are diamonds of large size, that it is stated that the whole number known to 
exceed 33 carats in weight does not exceed nineteen. 



Questions. — What is graphite ? In wbat conditions does it occur in nature ? What 
is said of its infusibility ? What of its practical applications ? 



286 INORGANIC CHEMISTRY. 

obtained, which is subsequently sawed into bars. . The particles of plumbago, 
although apparently very soft, are in reality extremely hard, and the steel 
saws employed to cut it rapidly wear out. Plumbago is also used for the 
manufacture of melting pots or crucibles, for the lubrication of the bearing sur- 
faces of machinery, and for imparting a luster to iron. 

Several modifications of graphite may be procured artificially. "When cast 
iron is melted with an excess of charcoal, it dissolves a portion of the carbon. 
This carbon, when the iron is allowed to cool slowly, crystallizes out in the 
form of large and beautiful leaflets of graphite. 

420. Gas Carbon . — Another exceedingly interesting variety of graphite 
is formed in the interior of the retorts used for the production of coal-gas. 
This substance (which may be procured in abundance at all gas-works) is 
known a3 " gas carbon." It possesses a luster resembling that of a metal, a 
hardness sufficient to enable it to scratch glass, and is one of the purest forms 
of carbon. 

421. Coal. — The third allotropic modification of carbon 
includes all the varieties of mineral coal, wood, dharcoal, 
lamp-black, soot, animal charcoal, etc., etc. 

422. Mineral Coal is the product of an accumulated 
vegetation, which flourished mainly during a particular 
period of the earth's history, known in geology as the 
" carboniferous epoch." 

It occurs on the earth in veins, or strata, enclosed between other strata of 
limestone, clay-slate, or iron ore. 

"We know that coal is of vegetable origin, because in every coal-mine wo 
find leaves, trunks, and fruits of trees in immense numbers, many of them in 
the- most perfect state of preservation ; so much so, that the botany of the 
coal period can be studied with nearly as much certainty as the botany of any 
given section of the present surface of the earth ; and, furthermore, whenever 
coal has not been too much changed by heat and pressure, a thin layer of it 
exhibits, under the microscope, all the ducts and vessels of the plant to which 
it originally belonged. 

Coal consists, like vegetable matter in general, of carbon, hydrogen, and 
oxygen, with a small proportion of nitrogen. It contains, in addition, variably 
quantities of saline and earthy substances, which always enter into the com, 
position of plants. These matters, when coal is burnt, are left unconsumedj 
and, together with some impurities, constitute its ashes. 

423. Anthracite Coal differs from bituminous in this respect — that 
its original volatile constituents, oxygen, hydrogen, etc., have been mainly 
driven off by the agency of heat, leaving carbon in a dense and nearly pure 

Questions. — How may graphite be formed artificially? What is gas carbon? What 
are its properties ? What is the third allotropic form of carbon ? What is mineral coal ? 
What proof have 'we of its vegetable origin ? What is the constitution of coal ? What 
occasiqns the difference between anthracite and bituminous coal? 



CARBON 



287 



condition behind ; bituminous coal, on the contrary, not having been exposed 
to the same degree of heat, retains its original vegetable constitution in a 
great degree unaltered.* When bituminous coal is ignited, its volatile con- 
stituents are expelled by heat, and burn with flame and smoke ; while an- 
thracite, from its previous deprivation of these substances, burns without flame 
or smoke. 

424. Coke is bituminous coal heated apart from air, until its volatile con- 
stituents are in a great measure expelled. It produces a more steady and 
intense heat than the coal from which it is derived, and evolves no smoke. 

425. Charcoal is that form of carbon which results from 
depriving animal and vegetable substances of their vol- 
atile constituents. 

This is usually effected by the agency of heat ; but the application of heat 
is not essential, since wood immersed in sulphuric acid, or buried for a long 
period in the earth, becomes converted into charcoal. 

Charcoal is usually j 1G , m \^ m 

prepared by firing wood 
in mounds or pits, cov- 
ered with turf or soil in 
such a way as to ex- 
clude in a great degree 
the admission of air, 
and thus prevent com- 
plete combustion. Fig. 
147 represents the ar- 
rangement and con- 
struction of a " charcoal 
mound or heap. " If the 
diameter of the heap be 30 feet or more, the operation is not complete in less 
than a month, and the slower the combustion the greater the product of 
charcoal. When the wood is thoroughly charred, the admission of air is en- 
tirely cut off, and the combustion ceases. The charcoal produced retains the 
form of the wood, but is much reduced in size ; generally not amounting to 
more than three fourths of the bulk of the wood, and never exceeding one fourth 
of its weight. The nicest kinds of charcoal, such as are used in the manufac- 
ture of gunpowder, are prepared by heating wood in close iron cylinders. | 

426. Soot is coal in a state of minute division resulting from the imper- 




* Wherever the strata inclosing coal have been disturbed and altered through th« 
agency of subterranean heat, the coal is generally anthracite ; but where the strata remain 
undisturbed, the coal is generally bituminous. Thus in Pennsylvania, the great coal-fields 
which are adjacent to the line along which the Appalachian chain of mountains have been 
elevated, furnish only anthracite ; but as we recede from the mountains and go west, the 
coal becomes bituminous. 



Questions. — What is coke? What is charcoal? How may it be prepared ? What i» 
the ordinary process of preparing charcoal ? What is soot ? 



288 INORGANIC CHEMISTRY. 

foct combustion of carbonaceous gases. Lamp-black is generally applied to 
designate the soot produced by the imperfect combustion of tar and resinous 
matters ; it is much used in the manufacture of printers' ink and of paint. 

Animal charcoal, bone-black, and ivory-black, are names given to the pro- 
ducts produced by heating bones, ivory shavings, and like animal substances, 
in close vessels. The charcoal thus obtained is mixed with ten times its 
weight of phosphate of lime. 

421. Properties , — Carbon in the form of charcoal is a black, brittle, 
insoluble, inodorous, tasteless substance. At ordinary temperatures it has 
little or no affinity for the other elements^ and is, consequently, one of the 
most unchangeable of all substances. Grains of wheat charred at Hercu- 
laneum nearly 2,000 years ago, still retain their form. "Wooden posts, if 
charred at the end before being set in the ground, are rendered far more dur- 
able. For the same reason, it is a common practice to char the interior of 
tubs and casks intended to hold liquids. 

Charcoal, when subjected to the action of the most intense heat, is infus- 
ible, and if air be excluded, it remains unchangeable.* 

At high temperatures, however, carbon surpasses all other bodies in its 
affinity for oxygen, and is, consequently, more suitable than any other sub- 
stance for depriving the metallic ores or oxyds of their oxygen, and reducing 
them to a metallic state — an operation termed smelting. 

The compounds of carbon with the other elements are termed carburets, or 
carbides. ' 

Newly prepared charcoal possesses the remarkable power of absorbing and 
condensing within its pores, large quantities of certain gases and aqueous va- 
por. (The explanation of this phenomenon has been already given, § 48.) 
Charcoal from hard wood, or that which possesses fine pores, exhibits this 
property in the highest degree, and the gases which are absorbed most abun- 
dantly are those which are most readily liquefied by cold and pressure ; 
thus of ammoniacal gas it absorbs 90 times its volume, of carbonic acid, 35 
times; of oxygen, 9 times; of hydrogen, 1-T5 volumes. 

Charcoal in a finely-divided state has also the power of absorbing odorifer- 
ous effluvia, and the coloring principles of most animal and vegetable sub- 
stances. Animal matter, in an advanced state of putrefaction, loses all offen- 
sive odor when covered with a layer of charcoal ; it continues to decay, but 
without emitting any ill odor. 



,:: An illustration of this is found in the fact, that charcoal thrown into a blast-furnace, 
and its access to air being cut off by an envelope of molten metal, will not unfrequently 
pass through the furnace unconsumed and unaltered. 

Questions. — What is lamp-black? What is animal charcoal ? What are the proper- 
ties of charcoal"? What is said of its indestructibility ? What of its affinities? Why is 
cai'bon uniformly used in the reduction of metallic ores ? What are the compounds of 
carbon with the metals called ? What is said of the absorbing power of charcoal ? What 
gases ar.e absorbed most abundantly ? What is 6aid of its deodorizing and decolorizing 
agency ? What are illustrations of its deodorizing action ? 



CARBON 



289 




Advantage has been taken of this property of charcoal to construct a res- 
pirator for protection against the inhalation of malarious and infected air. It 
consists of a hollow case of wire-gauze filled with coarsely -powdered charcoal, 
and fitted over the mouth and nostrils by Fig. 148. 

straps, as is represented in Fig. 148. All 
the air that enters the lungs must pass 
through this charcoal seive, and in so passing, 
is deprived of the noxious vapors or gases it 
may contain. For persons engaged in hos- 
pitals, dissecting-rooms, the holds of ships, or 
in the vicinity of sewers, this device is most 
valuable. Foul water filtered through a 
layer of powdered charcoal, is decolorized and 
purified. This action of charcoal may be il- 
lustrated by agitating water containing sul- 
phuretted hydrogen in solution, with a small 
quantity of freshly-burned powdered charcoal ; the offensive odor will com- 
pletely disappear. Sugar-refiners render brown sugar white by passing it in 
solution through animal charcoal. Ale and porter, subjected to the same 
Fig. 149. treatment, are not only decolorized, but deprived of 

/g\ their bitter principles. In case of poisoning with 

vegetable poisons, such as opium, morphia, strych- 
nia, etc., one of the best immediate antidotes which 
can be given is powdered charcoal in water : thia 
absorbs the poisonous principle, and renders it inac- 
tive. The decolorizing action of charcoal may be 
illustrated by filtering porter, port-wine, or water 
colored with ink, through a small quantity of animal 
charcoal. (See Fig. 149.) The filtered liquor will 
be deprived of smell, taste, and color. 

Charcoal loses its absorptive and decolorizing 
properties by use ; but on heating it afresh, it re- 
gains them. 

Carbon in the form of the diamond is a non-conductor of electricity ; but in 
all its other forms it is an excellent conductor, ranking next to the metals in 
this respect. In a state of fine subdivision, carbon is a bad conductor of heat, 
but its conducting power increases with its density. 

428. Compounds of Carbon and Oxygen . — The compounds 
of carbon with oxygen and hydrogen, and with oxygen, hydrogen, and nitro- 
gen, are innumerable, and constitute the great bulk of the substance of all 
vegetable and animal products. The consideration of these compounds be- 




Qtjestions. — What advantage has been taken of this property ? What are illustrations 
of the decolorizing action of charcoal ? Under what circumstances may charcoal act as aci 
antidote for poisons ? What is said of the conducting powers of carbon for heat and eleo- 
tricity ? What is said of the compounds of carbon with oxygen ? 

13 



290 



INORGANIC CHEMISTRY. 



longs mainly to organic chemistry. With oxygen alone carbon unites directly 
to form only two compounds — carbonic oxyd and carbonic acid. .Their com- 
position may be represented as follows : — 

Composition by weight. 



Pymbol. 

Carbonic oxyd CO 

Carbonic acid , CO2 



6 carbon. 
6 " 



+ 8 oxygen. 
-f 16 " 



429. Carbonic Acid, C 2 is the sole product of the com- 
bustion of pure carbon in oxygen gas or atmospheric air. 
It is also produced abundantly by all the ordinary pro- 
cesses of combustion, by respiration, fermentation, and by 
the decay of animal and vegetable products. It exists in 
a free state in the atmosphere, and in the earth in im- 
mense quantities, chiefly in combination with lime, form- 
ing carbonate of lime (marble, chalk, etc., etc.). 

For an account of its discovery see § 329. 

430. Preparation . — Carbonic acid may be prepared by burning char- 
coal in oxygen gas (p. 190) ; or by allowing a candle to burn as long as it 
will in a closed bottle or jar filled with air. Practically, however, it is ob- 
tained in a pure state, much "more conveniently. It being a feeble acid, 
almost every other acid, which dissolves freely in water, is able to expel it 
from its* compounds; it is, therefore, easily separated- from its compounds by 
the addition of any of the common acids. Thus, fragments of chalk .or_mar- 

ble, with a little water, are placed in an open-mouth bottle, or 
in an evolution flask (see Fig. 150, also Fig. 95), and diluto 
sulphuric or hydrochloric acid added. The acid seizes upon 
the lime, and displaces the carbonic acid, which escapes with 
an effervescence. It may be collected 
in the usual way over water, or in 
dry bottles, by the displacement of 
air. 

431. Properties. — At ordin- 
ary temperatures and pressures, car- 
bonic acid is a colorless, transparent _gas, of a 
pungent odor, and acidulous taste. It is more than half as 
heavy again as atmospheric air, its specific gravity being 
1-529 (air = 1*000); by reason of its great density, it may be ■ 
poured from one vessel into another like water. (See Fig. 
151.) 

Carbonic acid is not inflammable, and extinguishes the flame of burning 
bodies, even when largely diluted with air, for a candle will not burn in a 



Fig. 150. 




Fig. 151. 




Questions. — What is tbe composition of carbonic acid ? What is said of its formation 
and distribution ? How may it be prepared ? How is it obtained practically ? What are 
its properties ? What is said of its density ? What of its relation to combustion ? 



CARBON. 291 

mixture of 4 volumes atmospheric air, and 1 volume of carbonic acid.* This 
property may be strikingly illustrated by placing a lighted candle at the bot- 
tom of a deep jar, and then pouring carbonic acid from another vessel upon 
it, as is represented in Fig. 151. The light will be extinguished as soon as 
the gas reaches the flame. 

Carbonic acid in its pure state is irrespirable, producing, the moment it is 
inhaled, a spasm of the glottis, which closes at once the air passages of the 
lungs : an animal immersed in it, therefore, dies of suffocation. When di- 
luted with air, it may be breathed without difficulty, but if the proportion in 
{which it exists in the air exceeds 4 per cent., it acts as a narcotic poison.-j- A 
proportion of 10 to 12 per cent, is speedily destructive to animal life, and even 
so small a quantity as 1 or 2 per cent, is deleterious and depressing. The 
drowsiness and headache experienced in crowded and ill-ventilated apart- 
ments are chiefly due to the accumulation of carbonic acid as the resulting 
product of respiration. 

Many persons have lost their lives, either intentionally or by accident, by 
sleeping in a confined room with a pan of burning charcoal ; also from de- 
scending into wells, mines, vats, and sewers in which carbonic acid has accu- 
mulated. Accidents of the latter character may be prevented by taking the 
precaution to lower a lighted candle into the well or vat suspected to contain 
this gas, before descending into it ; if the light remains undiminished, all may 
be considered safe ; but if the flame be extinguished, or even sensibly im- 
paired, there is evident danger. "Wells, pits, etc., containing carbonic acid 
may be freed from it by lowering into them pans of recently-burned pulver- 



* This property of carbonic acid has been practically applied for the extinguishment 
of fires in coal-mines — a stream of carbonic acid, generated by passing air through a fur- 
nace of coal, being blown into the mine until all its passages were filled with it, and the 
combustion arrested. In this way, a coal-mine in England that had been on fire for thirty 
years, and had extended over twenty-six acres, was extinguished in 1851. About 8,000,000 
cubic feet of gas were required to fill the mine, and a continuous stream of impure car- 
bonic acid was forced in by the agency of a steam-jet, day and night, for about threo 
weeks. The difficulty lay not so much in putting out the fire, as in cooling down the ignited 
taass, so that it should not again burst into a flame on the readmission of air, and in order 
to effect the necessary reduction of temperature, water was blown in along with the carbonic 
acid, in the form of a fine spray, or mist Subsequently, cold air mixed with the spray 
was thrown in ; and in a month from the commencement of operations, the fire was found 
to be completely extinguished. 

A portable arrangement for extinguishing fires, termed the "Fire Annihilator," em- 
bodies the same principles. It consists, essentially, of a tin or sheet-iron case, containing 
a substance holding carbonic acid in combination, together with a bottle of sulphuric acid. 
By means of a simple arrangement, this bottle of acid maybe broken, when its contents, 
mixing with the solid, evolve carbonic acid ; and this, flowing out from apertures in tha 
case, fills the apartment, and extinguishes the fire. 

t By a narcotic poison we understand one which produces sleep and insensibility, ter. 
ruinating, if taken in sufficient quantity, in death. Opium and morphia are examples. 

Questions. — What of its relation to respiration ? "What are illustrations of the poison- 
ous influence of carbonic acid ? What precautions should be taken before descending into 
wells, sewers, etc. ? 



292 INORGANIC CHEMISTRY. 

ized charcoal, or fresh slacked lime, or by showering down cold water — all of 
which substances absorb the gas freely. 

To resuscitate those who have been exposed to the poisonous action of 
carbonic acid, dash cold water upon them freely, and assist the circulation by 
friction of the extremities. 

432. "Water at ordinary temperatures and pressures absorbs about two 
thirds of its bulk of carbonic acid ; but it will take up much more if the pres- 
sure be increased. The quantity absorbed is in exact ratio with the compres- 
sing force, the water dissolving twice its volume when the pressure is doubled, 
and three times its volume when the pressure is trebled. On removing the 
pressure the greater part of the gas escapes, and produces that effervescence 
which we see when a bottle of ginger-beer, soda-water, cider, or champagne 
is opened. 

Most of the beverage sold under the name of soda-water does not contain 
a particle of soda, but is merely water impregnated, by mechanical pressure, 
with about eight times its bulk of carbonic acid. In fermenting liquors in- 
closed in bottles, on the contrary, the carbonic acid is gradually evolved by 
the process of fermentation in the interior of the bottle. As fast as it is set 
free, the liquor dissolves it, the pressure of the gas upon the inner surface of 
the bottle increasing at the same time. The pressure thus generated is enor- 
mous, and beyond a certain limit the cork will either be forced out, or the 
bottle will burst. If the cork be withdrawn, the confined gas will drive out 
the liquor in its own eagerness to escape. The manufacture of champagne is 
always carried on in vaults far below the surface of the earth, in order to 
secure a low, and at the same time a uniform temperature. The reason of thi3 
is, that the absorption of carbonic acid by the liquor is greatly assisted by a 
reduction of temperature, and a rise of a few degrees of the thermometer in 
the vault is sometimes accompanied by the breakage of thousands of bottles. 

Fermented liquors, by the escape of their carbonic acid, are rendered flat 
and insipid. A thick, viscid, or glutinous liquor, like porter or ale, retains 
the little bubbles of carbonic acid as they rise through it, and is thereby 
caused to froth ; but a thin liquor, like champagne or cider, which allows the 
bubbles to escape freely, only sparkles. 

A solution of carbonic acid in water has a pleasant, acid taste, and tem- 
porarily reddens blue litmus paper. The solvent powers of such a solution 
are far more extensive than those of pure water ; and the hardest rocks and 
minerals are gradually disintegrated and broken down by the long-continued 
action of water charged with a small proportion of this gas. 

433. Solidification of Carbonic Acid.— When carbonic 
acid at 32° F. is subjected to a pressure of 36 to 38 at- 

Qtjesticxns. — "What is the antidote against poisoning with carbonic acid ? What is said 
of the absorption of carbonic acid by water ? What is ordinary " soda-water?" What is 
the source of carbonic acid in fermenting liquors ? What takes place when a fermenting 
liquor is bottled ? When does a liquor froth, and when sparkle? What is said of the 
solvent power of carbonic acid in solution ? What is said of the solidification of carbonia 
vnd? 



CARBON. 



293 



mospheres, it condenses into a liquid as transparent and 
colorless as water. If a stream of liquefied acid be allowed 
to escape into the air, it freezes by its own evaporation 
into a white, snow-like solid.* 

* The compressing force used to effect the liquefaction of carbonic acid is that of the 
elasticity of the gas itself. The experiment may be performed by generating carbonic 
acid in a closed glass tube, as has been previously explained (see § 178) ; but usually an 
apparatus constructed for this particular purpose is employed. This consists of two cyl- 
indrical vessels, Fig. 152, each of -wrought iron, and each sufficiently strong to withstand 

Fig. 152. 




a pressure of 4,000 lbs. per square inch. One of these vessels serves as a generator, and 
the other as a receiver, and both are furnished with stop-cocks of a peculiar construction. 
The generator is furnished with an axis, and is mounted upon an iron frame, so that it 
may revolve in a vertical plane. The receiver is supplied with a tube, which goes nearly 
to the bottom, and the generator with a cylindrical copper vessel which admits of being 
filled with oil of vitriol. 

The operation is conducted by charging the generator with a solution of bi-carbonato 
of soda, and the copper vessel with sulphuric acid. The stop-cock of the generator being 
now firmly closed, the generator itself is revolved upon its axis, by which means the oil 
of vitriol contained in the copper vessel runs out upon the carbonate of soda, and occa- 
sions a liberation of carbonic acid. After a time, when the action is complete, the re- 
ceiver, which is immersed in a freezing mixture, is connected by means of a metallic tube 
with the generator, and the stop-cocks being opened, the carbonic acid contained in the 
generator rushes over into the cold and empty receiver, and becomes in part condensed. 



Question — Give a general description of the process. 



294 



INORGANIC CHEMISTRY 



In this condition it wastes away slowly, and may be handled and molded 
with ease. If suffered to remain in contact with the skin, however, it burns 
like a red-hot iron. 

"When a little mercury is placed in a porcelain cup and covered with solid 
carbonic acid, the addition of a few drops of ether occasions so rapid an 
evaporation that the mercury is immediately frozen, and may then be ham- 
mered and drawn out like lead. In this way ten pounds of mercury may bo 
frozen in less than eight minutes. 

434. Lime-water brought in contact with carbonic acid gas rapidly absorbs 
it, and becomes milky from the formation of carbonate of lime (chalk). This 
reaction, therefore, constitutes a test for the presence of carbonic acid. 
Thus if we expose fresh lime-water to the air, a pellicle of carbonate of lime 

p _ soon forms upon its surface, proving the pres- 

ence of carbonic acid in the atmosphere. In 
like manner, by blowing through a tube (see 
Fig. 153) into a vessel of lime-water, we can 
demonstrate the abundant presence of carbonic 
acid in the air expelled from the lungs. The 
milkiness occasioned by the contact of car- 
bonic acid with lime-water, disappears when 
an additional quantity of acid is taken up by 
the solution — carbonate of lime being soluble 
in an excess of carbonic acid. Many natural 
waters, by virtue of an excess of carbonic 
acid contained in them, hold very considerable 
quantities of lime in solution, and are thereby 
rendered " hard." "When such waters are heated or agitated with air, a portion 
of the carbonic acid escapes, and the lime is precipitated — forming in boilers 
and tea-kettles, and in the channels of streams, incrustations of lime. 

435. Petrifactions . — It often happens, when an organic substance 
is placed in water holding lime in solution by virtue of an excess of carbonic 
acid, or other mineral matter, that its particles, as they decay, are replaced 
by particles of mineral matter, until at last all the organic particles disappear, 
and a stony mass is substituted, which resembles the original substance in 




The stop-cocks are now closed, the vessels disconnected, and the generator opened and 
freed of its contents. It is then charged afresh, and the operation repeated as hefore ; five 
or six repetitions being necessary before any very considerable quantity of liquefied acid 
becomes accumulated in the receiver. 

The liquefied gas can be drawn off from the receiver by means of a jet, a, screwed on 
to its stop-cock. When a portion is discharged by means of this jet into a metallic box, 
b, fitted with perforated wooden handles, a part of the liquid gas assumes a 6olid condi- 
tion in consequence of the intense cold developed by the evaporation of another portion, 
and the box becomes filled with a white solid, like -dry snow 



Questions.— What are the properties of the solidified gas? What is a test for the 
presence of carbonic acid? What are illustrations? Under what circumstances does 
carbonate of lime dissolve in water ? When is it deposited ? What are petrifactions ? 



CARBON. 295 

form and structure, and not unfrequently in color. This result is termed 
petrifaction. It is a mistake, however, to suppose that the original particles 
are converted into stone ; for the process of petrifaction is one of replace- 
ment, and not of conversion, i. e., a particle of mineral matter of the same 
form being substituted for each organic particle. 

436. The presence of carbon in carbonic acid may be demonstrated by drop- 
ping a piece of ignited potassium into a small flask filled with the dry gas. 
The potassium, by depriving the carbonic acid of its oxygen to form potash, 
liberates carbon, which is deposited in the form of black particles upon the 
walls of the glass. This experiment, which is a very striking one, may also 
be performed by igniting a bit of potassium in a glass tube, through which 
a current of dry carbonic acid is at the same time transmitted. 

43 7. Carbonic acid is evolved from the earth in many localities, particu- 
larly in volcanic districts. At one locality near Vesuvius in Italy, it is esti- 
mated that 600 lbs. weight are discharged every twenty-four hours. 

438. The salts formed by the union of carbonic acid with the protoxyds 
of the metals, are numerous and important, and are termed Carbonates. 
They are easily decomposed by contact with the stronger acids, and, with 
the exception of the carbonates of the alkalies, they are for the most part in- 
soluble in water. 

439. Carbonic Oxyd, CO. — When carbonic acid is passed 
over red hot coal, or metallic iron, it loses half of its oxy- 
gen, and becomes converted into carbonic oxyd. 

This reaction is often witnessed in coal fires. The fuel in the lower part 
of the grate, which has free access to air, generates by its combustion carbonic 
acid. This passing up through the interior of the fire, where the supply of 
air is limited, is deprived of half of its oxygen, and becomes carbonic oxyd, 
while at the same time the carbon of the heated fuel which has entered into 
combination with the removed oxygen furnishes another equal quantity of the 
same gas. On coming in contact with the air at the top of the fire, the car- 
bonic oxyd ignites, and burns with a flickering, pale-blue flame. This phe- 
nomenon may be particularly noticed in a charcoal fire, when fresh coal has 
been recently added. 

Carbonic oxyd is a transparent, colorless gas, which is much more poison- 
ous than carbonic acid ; and the inhalation of air containing one two hun- 
dredths of it, for any considerable length of time, is said to be fatal. Carbonic 
oxyd may be obtained with* facility by heating crystaUized oxalic acid with 
five or six times its weight of concentrated sulphuric acid in a glass retort, 
and collecting over water. As thus prepared, it contains carbonic acid, from 
which it may be separated by allowing the mixed gases to bubble through 
milk of lime, or solution of potash. 

Qttestiosts. — How may the presence of carbon in carbonic acid be demonstrated ? What 
is said of the natural production of carbonic acid ? What of its salts ? W T hat is carbonic 
oxyd ? What is a familiar example of its production ? What are the properties of car- 
boaic oxyd ? How is it prepared ? 



296 



INORGANIC CHEMISTRY. 



Fig. 154. 




By generating the carbonic oxyd in the same manner in a test tube fitted 
with a perforated cork and jet, Fig. 154, the gas may be 
ignited as it is evolved, and its peculiar blue flame ex- 
hibited. 
440. Carbon and Sulphur. 
Bi -Sulphide of Carbon, CS 2 . — When frag- 
ments of sulphur are dropped upon ignited charcoal 
contained in a peculiarly arranged earthen retort, the 
sulphur in the form of vapor unites with the carbon, and 
the product of the combination distilling over, may be 
condensed, in cooled receivers, into a colorless, transpa- 
rent liquid — bi-sulphide of carbon. 

This compound is highly volatile and inflammable, and 
is characterized by a most foetid and peculiar odor. It 
possesses the power of refracting light in a remarkable 
manner, and as the most ready solvent known of gutta-percha, India-rubber, 
and various greasy and resinous substances, it is somewhat extensively ap- 
plied to manufacturing purposes. It also dissolves sulphur, phosphorus, and 
iodine — these bodies being deposited again in beautiful crystals by the evapo- 
ration of their solvent. 
441. C a r b on and Nitrogen. 

C yan ogen, NC2 or Cy . — This substance, which is one of th^, most 
interesting compounds of carbon, strikingly resembles an element, and was the 
first compound body which was distinctly proved to be capable of entering 
into combination with the elements in a manner similar to that in which the 
elements combine with each other. 

This discovery, made in 1814 by Guy Lussac, formed an epoch in chemical 
science, and by originating new views of chemical composition, revolution- 
ized the whole subject of organic chemistry. Since then, numerous other 
bodies have been discovered, which deport themselves in respect to the ele- 
ments exactly as cyanogen does — or in other words, as if they themselves 
were elements. Such compound bodies are known in chemistry as compound 
or organic radicals; — the elements being simple radicals. (See § 211.) 

The name cyanogen (blue-producer, from the Greek Kvavo^ blue) is derived 
from the circumstance that this body forms an essential ingredient in the pig- 
ment, " Prussian Blue." 

Cyanogen consists of 2 equivalents of carbon, and 1 of nitrogen ; but no 
direct union of these elements can be effected. 

For experimental purposes on a small scale, it may be obtained by heating 
in a small retort, or test tube (see Fig. 155), the salt known as cyanide of 
mercury, previously reduced to a fine powder, and well dried. The cyanide 



Questions. — "What is bisulphide of carbon? What is its method of preparation? 
What are its properties ? What its practical applications ? What is said of cyanogen ? 
What are compound or organic radicals ? What in chemistry is understood by a radical? 
What is the chemical constitution of cyanogen ? How may it be prepared ? 



CARBON. 



297 




undergoes decomposition, like the oxyd of mercury under FiG. 155. 

the same circumstances (§ 281), yielding metallic mer- 
cury and gaseous cyanogen, which should be collected 
over mercury. 

412. Properties . — Cj^anogen is a transparent, col- 
orless gas, with a pungent, peculiar odor, somewhat resem- 
bling that of peach kernels ; it is nearly twice as heavy 
as atmospheric air, and when inhaled, is poisonous. It is 
inflammable, and burns with a beautiful and character- 
istic purple flame. At a temperature — 1° F., it liquefies, 
and forms a colorless, limpid liquid, which freezes at 
— 30° F. into a transparent solid. 

Cyanogen in many of its properties closely resembles 
chlorine, and like it unites with hydrogen to form an 
acid, and with the metals to form salts, termed cyanides, 
which latter possess the characteristic properties of the haloid salts. 

443. Ferrocyanide of Potassium, K 2 , F e C y 3 -f 3 H . — 
Prussiate of Potash. — The compounds of cyanogen are almost always obtained 
from a salt known as ferrocyanide of potassium, or yellow prussiate of potash, 
which is a double cyanide of potassium and iron. This salt is prepared on a 
large scale, by heating in a covered iron pot or retort, about 5 parts of refuse 
animal matter, such as the parings of hoofs, horns, hides, dried blood, etc., 
with 2 parts of carbonate of potash (pearlash), and iron filings. At a high 
temperature the nitrogen and carbon of the animal substances react upon 
each other, and form cyanogen, which combines with potassium derived from 
the potash, and with iron. On digesting the mass, when cold, with water, 
the ferrocyanide of potassium (K2, Fe Cy3-j-3 HO) is formed, and may be ob- 
tained, by filtering and evaporating the solution, in splendid, yellow, flat 
crystals. In this condition it forms an important article of commerce. 

444. Prussian Blue . — "When a solution of ferrocyanide of potassium 
is added to a solution of peroxyd of iron,* a beautiful, deep-blue, bulky pre- 
cipitate is obtained, which, when washed and dried, constitutes the well- 
known pigment, Prussian, or Berlin blue — so called from its discovery at 
Berlin, in Prussia, in 1110. This substance is largely used in painting, in 
calico-printing, and dyeing, in staining wood and paper, and for concealing or 
neutralizing the yellow color of linen (an operation termed blueing). Cloth 
may be dyed blue by first immersing it in a solution of peroxyd of iron, and 
then in one of ferrocyanide of potassium ; the two substances thus meeting 
in the structure of the cloth, precipitate or produce the color in the very in- 
terior of the fibers. 



* A solution of peroxyd of iron may be readily obtained by dissolving a few crystals of 
copperas (green vitriol) in water, adding a little nitric acid, and beating tbe solution. 



Questions. — What are its properties? What is said of its affinities and compounds? 
What is ferrocyanide of potassium ? How is it prepared ? How is Prussian blue pre- 
pared ? What are its uses? How is cloth dyed of this color ? 



V 



298 INORGANIC CHEMISTRY. 

445. Blue Ink . — Prussian blue is insoluble in water and in dilute acids, 
with the exception of oxalic acid. The blue liquid obtained from its solution 
in this acid, thickened with gum, constitutes the well-known blue ink, or 
writing fluid. 

The color of Prussian blue is not very permanent, and is instantly destroyed 
by the action of the alkalies. The substance itself is formed by the union 
of cyanogen with iron; and its composition, which is somewhat complex, 
may be represented by the formula (3 Fe Cy-j-2 Fe 2 Cyz). Although con- 
taining cyanogen, a poison, Prussian blue is not poisonous, and is used by 
the Chinese in large quantities for the coloration of "green tea."* 

"When ferrocyanide of potassium is added to a solution of protoxyd of iron 
(green vitriol), it occasions a greenish- white precipitate, which, by exposure 
to air, rapidly becomes blue. 

Fcrridcyanide of Potassium . — When chlorine gas is passed 
through a solution of ferrocyanide of potassium, a salt crystallizing in ruby red 
crystals is obtained, which contains a larger proportion of cyanogen than the 
ferrocyanide of potassium ; and is known as the ferridcyanide of potassium, 
or the red Prussiate of potash. When added to a solution of the protoxyd of 
iron, it produces a dark-blue precipitate, but with solutions of the peroxyd it 
forms no precipitate. By the use, therefore, of the ferro and ferrid cyanides 
of potassium, chemists are easily able to distinguish between salts of the per- 
oxyd and salts of the protoxyd of iron. 

446. Cyanide of Potassium, KCy . — When 8 parts of ferro- 
cyanide of potassium, 3 of carbonate of potash, and 1 of charcoal, are exposed 
to a strong red-heat in an iron crucible, a compound of cyanogen and potas- 
sium is obtained— the cyanide of potassium. This salt, when pure, somewhat 
resembles white porcelain in appearance ; it is freely soluble in water, and 
when taken into the stomach, is a deadly poison. The hands of the work- 
men who use this salt are also liable to ulceration. 

The solution of cyanide of potassium in water possesses the property of dis- 
solving most of the metallic oxyds, especially those of the precious metals ; it 
is, on this account, therefore, extensively used for the preparation of the gold 
and silver solutions employed in electro-gilding and plating. A solution of 
cyanide of potassium will dissolve out the black marks of "indelible ink," 
which is a solution of the oxyd of silver. 

447. Hydrocyanic Acid, My. — Prussic Acid. — This 
compound, so remarkable for its poisonous properties, is 



* The progress of chemical science is strikingly illustrated by the fluctuations in the 
price of this pigment ;— thus in 1770, its price was $10 perpound ; in 1815, $3; in 1825, 
60 cents ; and at the present time, about 30 cents. 

Questions. — What is blue ink ? What is said of the permanency of the color of Prus- 
sian blue ? What is its composition ? What is the reaction of ferrocyanide of potassium 
and protoxyd of iron ? What is ferridcyanide of potassium ? What are its reactions with 
the solutions of the oxyds of iron ? How is cyanide of potassium formed ? What are its 
properties ? What its practical applications ? What is said of the formation of prussic acid ? 



CARBON. 299 

formed by the indirect union of cyanogen and hydrogen. 
It is easily obtained by distilling cyanide of potassium 
with dilute sulphuric acid. 

The reaction is similar to that involved in the production of hydrochloric 
acid from common salt and sulphuric acid (§ 358), thus: — 

Cyanide of potassium. Sulph. acid. Sulph. potash. Hydrocyanic acid. 

KCy + S0 3 , HO = KO, SO3 -f- HCy. 

In its pure state, hydrocyanic acid is a colorless, transparent liquid, with a 
feeble acid reaction. It is lighter than water, and so extremely volatile, that 
if a drop be allowed to fall upon a glass plate, a part of the acid will be frozen 
by its own evaporation. Its vapor has an odor of peach-blossoms or bitter 
almonds, and both of these substances owe their peculiar flavor in part to the 
presence of this acid in their composition. 

Hydrocyanic acid is the most fatal of all the poisons known to the chemist. 
A single drop of the concentrated acid upon the tongue of a large dog pro- 
duces immediate death ; and a slight inhalation of its vapor occasions very 
disagreeable sensations. "When largely diluted with water, it is sometimes 
given in medicine in very minute doses. Ammonia, brandy, and chlorine 
are its best antidotes. A suspension of animation occasioned by an over-dose 
of it does not always result in death, if proper remedies are employed. 

Physiologists are not fully agreed as to the cause of the almost instantan- 
eous death occasioned by this acid. By some it is supposed to act upon the 
vital organs by reason of a sympathetic shock transmitted to the nerves ; and 
by others the effect is ascribed to an almost immediate absorption of the poison 
into the system. 

Various parts of many plants belonging to the order Bosacece, such as bitter 
almonds, the kernels of plums and peaches, the leaves of the cherry-laurel, 
etc., yield, on distillation with water, a sweet-smelling liquid containing hy- 
drocyanic acid. 

448. Cyanogen and Oxygen • — Cyanogen further resembles an 
element in the circumstance that it is capable of uniting with oxygen, in sev- 
eral proportions, to form acids, which, in turn, unite with bases to produce 
salts. The two best known of these oxyds, cyanic and fulminic acids, have 
an identity of chemical constitution, but entirely different properties. . 

449. Cyanic Acidj CyO is a highly volatile liquid, which decomposes 
quietly, but so readily, that, it is exceedingly difficult to preserve it in unal- 
tered condition ; its salts are termed cyanates. 

450. Fulminic Acid, C y 2 2 , which, like cyanic acid, is composed 
of equal atoms of cyanogen and oxygen, is not known in a separate state. Its 
compounds with the metallic oxyds are termed fulminates, since they explode, 

Qtjkstions. — What chemical reaction is involved in its preparation? What are the pro- 
perties of prussic acid ? "What is said of its poisonous qualities ? What are its antidotes? 
How is it supposed to occasion death? From what vegetable productions may prussie 
acid be obtained ? In what other respects does cyanogen resemble an element ? What 
is said of cyanic acid ? What of fulminic acid ? 



300 INORGANIC CHEMISTRY. 

from the slightest disturbing causes, with fearful violence. The compound 
with mercury, termed " fulminating mercury," is prepared by dissolving 1 
part of mercury in 12 parts of nitric acid, and mixing the solution with an 
equal quantity of alcohol ; on the application of gentle heat, chemical action 
ensues, accompanied by the evolution of copious white fumes, and the fulmin- 
ate separates in white crystalline grains. As thus obtained, it constitutes, 
when mixed with six times its weight of saltpeter, and made into a paste 
with water, the composition used for filling percussion caps. 

Besides the fulminate of mercury, analagous compounds may be formed in 
a similar manner with oxyds of silver, copper, zinc, and other of the elements. 
All of them are exceedingly dangerous to handle, and the fulminate of silver 
ranks next to the chloride of nitrogen in explosive character ; thus, it explodes 
under water when heated to 212° F., and also when in a moist state by fric- 
tion with a hard body ; when dry, the touch of a feather, or the vibration of 
the house occasioned by the rolling of a carriage, is also sufficient to cause its 
violent decomposition. The fulminic acid separates, "on exploding, into nitro- 
gen, carbonic oxyd, and the vapor of water, the metal being set free.* 

451. Compounds of Carbon and Hydrogen. — The com- 
pounds of carbon with hydrogen are numerous, and are 
all derived from the decomposition of bodies of an or- 
ganic origin. Some of these are liquid, some solid, and 
others are gaseous. 

The consideration of two of them only properly pertains to the department 
of inorganic chemistry. These are, light carburetted hydrogen gas, C2H4, and 
heavy carburetted hydrogen, or Olefiant gas, C4II4. 

452. Light Carburetted Hydrogen, C 2 H 4 . — Marsh Gas ; Fire- 
damp. — This gas occurs abundantly in nature. It is evolved from rock-fissures 
in coal mines, and forms, in connection with atmospheric air, an explosive 
compound, known to the miners as " fire-damp."f It is also a constant product 
of the putrefactive decomposition of wood and other carbonaceous bodies un- 
der water, and may be obtained from this source by stirring the mud at the 
bottom of stagnant pools, and collecting the gas as it rises by means of an 
inverted bottle and tunnel. (See Fig. 155.) At Kanawha, in Virginia, this 
gas rises in immense quantities in connection with salt-water from Artesian 



* The detonating bombs with which the life of Napoleon III. was attempted in 1853, 
were filled with fulminating mercury. 

t In this condition it accumulates in the galleries of coal mines in large quantities, and 
when fired by accidental contact with flame, explodes with fearful violence. The product 
of the explosive combustion is mainly carbonic acid, so that the workmen in the mine who 
escape death by burning, are almost certain to be afterward suffocated. By an explosion 
of this character at the Felling colliery in England, in 1812, 92 persons lost their lives. 
These accidents have now been in a great measure prevented by the use of the " safety 
lamp." 

Questions. — How is fulminating mercury prepared ? To what use is it applied ? 
What is said of the other fulminates ? "What is said of the compounds of carbon and hy- 
drogen ? What is said of light carburetted hydrogen ? What is " fire-damp ?" 



CARBON. 



301 



Fig. 155. 




10O 



wells, and being conducted by an ar- 
rangement of pipes under the salt- 
boilers, furnishes sufficient heat by 
its combustion to evaporate the brine. 
A similar natural supply of this gas 
in the town of Fredonia, in New 
York, has for many years past been 
extensively applied for illuminating 
purposes. 

453. Properties . — Light car- 
buret ted hydrogen is a colorless, in- 
odorous, tasteless gas, slightly soluble 
in water, and when diluted with 
common air may be inhaled with- 
out injury. Its weight is about half 
that of air. It does not support com- 
bustion, but is itself inflammable, and 
burns with a yellow, luminous flame. 

"When mingled with air or oxygen gas it forms explosive compounds, 
parts of this gas by weight, consist of 75 carbon and 25 hydrogen. 

454. Heavy Carburetted Hydrogen. Olefiant Gas, CJI4. 
— This gas was discovered in 1796 by an association of Dutch chemists, who 
gave it the name of " olefiant" (oil-producer), from its formation with chlorine 
of a compound having the appearance of oil. It does not occur naturally, 
but is obtained by the destructive distillation* of oiL and also in connection 
with light carburetted hydrogen and some other substances, when coal, resin, 
tar, asphaltum, fat, animal refuse, and similar inflammable matters are distilled 
for the purpose of obtaining gas for artificial illumination. 

Olefiant gas is easily prepared by heating to- 
gether 1 measure of strong alcohol with 2 meas- 
ures of oil of vitriol in a retort or flask capable of 
holding at least four times the bulk of the liquid 
introduced. (See Fig. 156.) The gas comes off 
freely at first, but by degrees the mixture black- 
ens and froths up, so that a careful regulation of 
the heat is necessary. It is accompanied by the 
_L_ vapor of ether, and toward the close of the pro- 
§| cess by sulphurous acid in large quantities ; but 
it may be purified by causing it to pass, first 
through a "Woulfe's bottle containing a solution 
of potash, then through oil of vitriol, and finally 
collecting over water. 

* By destructive distillation, we understand the decomposition of a body subjected to 
heat in a retort, accompanied by a partial or entire volatilization of its products. 

Questions. — What are its properties ? What is said of olefiant gas ? How is it ob- 
tained ? What is understood by destructive distillation ? 



FIG. 156. 




302 INORGANIC CHEMISTRY. 

455. Properties . — Olefiant gas, as thus prepared, is a colorless gas, 
with a faint, sweetish odor. It is slightly soluble ia water, and has about the 
same density as air. It was liquefied by Faraday under great cold and pres- 
sure, but remained unfrozen at — 166° F. 

Olefiant gas does not support life or combustion, but is itself very inflam- 
mable, and burns with a splendid white fight, far surpassing in brilliancy 
that produced by light carburetted hydrogen. When mixed with oxygen 
and fired, it explodes with great noise and violence. This may be illustrated 
by passing bubbles of the mixed gases through water, and igniting them at 
the surface, care being taken not to communicate fire to the vessel containing 
the mixture. 

The composition of olefiant gas is 2 volumes of hydrogen and 2 of carbon 
vapor condensed into 1 volume. 

"When olefiant gas is mixed over water with an equal volume of chlorine, 
the two gases gradually unite, and form a heavy, sweetish, aromatic liquid. 
This substance, which collects in oily-looking drops in the water, is commonly 
known as " Dutch liquid," from its discoverers. 

An instructive experiment may be also performed by mixing in a tall jar 2 
measures of chlorine and 1 of olefiant gas. On applying a light to the mouth 
of the vessel, the mixture burns quietly — the chlorine uniting with the hydro- 
gen to form hydrochloric acid, while the carbon is deposited in the form of a 
dense black smoke. — l 

456. Illuminating Gas, prepared by distilling in close I 
vessels bodies rich in hydrogen and carbon, but deficient 
in oxygen, is always a mixture of olefiant gas, li ght nar^_ 
buretted hydrogen, carbonic -oxyd, and hydrogen in va- 
riable proportions, depending upon the nature of the sub- 
stance, and of the process of manufacture. 

The most valuable constituent of all illuminating gases,J& olefiant gas ; and 
if this gas could be procured sufficiently cheap, it would be used alone in 
preference to all others ; but as this is not the case, we are obliged, from mo- 
tives of economy, to be content with a mixture of olefiant and other gases, 
such as is yielded by the decomposition of oils, fats, resins, coals, and the like 
substances. Oils and fats, when distilled, yield a product very rich in ole- 
fiant gas, which has double the illuminating power of the best coal gas, and 
three times that of ordinary coal gas. Resins also yield a highly illuminating 
gas.. The first cost, however, of oil and resin is so much greater than that 
of coal, that the former are not able in an economical point of view, to com- 
pete with the latter, although the product of gas from coal is every way in- 

Questions.— What are its properties? What is said of the illuminating properties of 
olefiant gas ? What compound does it form with chlorine ? What phenomena attend its 
combustion with chlorine ? What is illuminating gas ? What is its most valuable con- 
stituent ? What are the comparative values of oils, resins, and coals for the manufacture 
of gas? 

La- 



\ 



CARBON. 



303 



ferior to that from oil and rosin. Fig. 15*7. 

Thus a pound of coal yields from 
3 to 4 cubic feet of gas ; a pound of 
oil, 15 cubic feet; of tar, 12; and 
of resin, 10. 

451. Coal G a s is only produced 
from the bituminous varieties of 
coal, but all bituminous coals are 
not fitted for gas manufacture. The 
production of gas depends upon the m 
application of a high temperature to 
the coaL At a moderate heat, such 
as 400° F., the volatile constituents 
of the coal separate mainly as liquids 
— oil and tar — with little or no ad- 
mixture of permanent gas ; but at 
a cherry-red heat, or a little higher, 
there is an abundant production of 
gas, with only a small production 
of tar, etc. That variety of coal 
known as "cannel," is far superior 
to all others for the production of 
gas. 

The manufacture of coal gas is 
divided into three processes, viz., its 
formation, purification, collection 
and distribution. 

Its formation is always ef- 
fected in semi-cylindrical 
tubes of cast-iron, called re- 
torts, arranged in furnaces, 
as is represented at R F, 
Fig. 157. The cylinders are 
closed at the posterior end, 
and open in front, each being 
provided with a door, which 
is made to fit air-tight by 
means of screws and moist 
clay. In very extensive 
gas-works there are from 
40,0 to 500 retorts, of which 
from 200 to 300 are worked night and day — each retort being charged with 
about 120 lbs. of coal every 6 hours. The residue left in the retorts after all 

Qttestiosts. — What coals are used for gas manufacture? Upon what does the produc- 
tion of gas from coal depend? Into what three processes is gas manufacture divided T 
Describe the formation of coal gas. 




304 



INOKOANIC CHEMISTRY. 



the volatile products of the coal have been evolved, is coke, which is raked 
out, cooled, and used for fuel. It is worth, for heatin ^purposes, as much or 
more than the coal originally was from which it is derived, and, therefore, 
the cost of the coal used in the retorts is, theoretically, nothing. Fig. 158 
represents the manner, of charging and clearing the retorts, and the general 
appearance of the furnaces of large gas-works. 

Fig. 158. 




The volatile products evolved by boat from the coal are light and heavy 
earburetted hydrogen, carbonic oxyd, hydrogen, oily vapors, sulphurous acid, 
sulphuretted hydrogen, ammonia, carbonic .acicL. aqueous vapor, nitrogen, and 
small quantities of many other substances. This mixture is totally unfit for 
illuminating purposes until purified, which is accomplished as follows : — 



Question — What are the volatile products evolved from the coal ? 



CARBON. 305 

The gases and vapors, as they are evolved from the coal, flow out of the 
retorts through iron pipes into a receiver half filled with water, which is 
called the hydraulic main, H, Fig. 157 — the extremities of the pipes dipping 
beneath the surface of the water, in order to prevent the gas from returning 
into the retorts when the doors are opened. In the hydraulic main a consid- 
erable quantity of the matters volatilized with the gas are deposited, viz., 
ammonia and the oily vapors, which condense into a black, semi-liquid mass, 
known as "^coal-tar." The gaseous products, however, being still hot, retain 
various other matters in a vaporous state, which, unless separated, would in 
cooling condense in distant parts of the apparatus, and stop up the pipes. 
The hot gas is therefore made to pass from the hydraulic main into large up- 
right iron tubes, surrounded with cold water, which are called condensers, 
in which the remaining vapors condense into a liquid, and trickle down into 
reservoirs provided for their reception, C, Fig. 157. From the condensers, 
the gas passes through a cylindrical vessel, P, Fig. 157, filled with cream of 
lime, kept in a state of constant agitation by means of a wheel, or stirrer, s s. 
This lime removes the carbonic acid, the sulphur compounds, and the re- 
maining ammonia from the gas, which is then discharged into the gasometer, 
and is ready for distribution. 

Dry lime arranged upon a series of shelves, over which the gas is made to 
pass, is also used for purification. As the gas leaves the lime-purifiers, the 
aqueous vapor which it always contains in a greater or less quantity, takes 
up mechanically certain portions of the lime ; each little particle being in- 
closed in a microscopic vesicle or bubble of vapor, which floats in the gas 
with its burden like a miniature balloon. In the combustion of the gas these 
vesicles of vapor burst, and their inclosed particles of lime being liberated, 
occasion the sparkling which may be generally observed in the flame of coal 
gas. 

In the beginning of the distillation, the defiant gas forms about one fifth 
of the entire volume, but toward the end of the process, or by too strong a 
red-heat, its quantity considerably diminishes, while that of hydrogen increases. 
The great bulk of ordinary coal gas is light carburetted hydrogen ; the gas 
first given off from good coals consisting of 13jp£n!eiLant gas, 82/5 carburetted 
hydrogen, 3*2 carbonic oxydj and l - 3 nitrogea After the lapse of 5 hours 
the product consists of _7_ olefiant gas,J56 carburetted hydrogen, JJ^. carbonic 
oxyd, 21*3 hydrogen, and 4jL nitrogen. The free hydrogen and carbonic 
oxyd present in coal gas give no light, and are positively injurious, by dilut- 
ing the illuminating gases. 

Gas is sold by the cubic foot, or by the thousand cubic feet ; and an ordi- 
nary gas-flame is generally estimated to consume from 1 to 1^- cubic feet per 
hour. ~ s -— , — 

458. Gas Meters , — G-as is measured by means of a self-acting instru- 

Questions. — How is the gas purified ? What proportion of coal-gas is olefiant ? What 
proportion is light carburetted hydrogen ? How is gas sold ? How much gas will an or- 
dinary burner consume in an hour ? How is gas measured ? Describe the construction 
of the meter. 



306 INORGANIC CHEMISTRY. 

merit called a meter. Its principle of construction and working may be illus- 
trated as follows: When a number of vessels, of known capacity, are so 
arranged that (without loss of gas in the interval) one after the other shall be 
filled by gas in passing — and for this purpose, are inverted in water, into 
which the gas enters, as in the case of an ordinary gasometer — it follows, that 
just as many cubic feet will have passed as there are vessels that have been 
filled. If all these vessels are attached to a common axis and revolve with 
it, as each in succession fills and rises, the axis will be turned once round, 
Fig. 159. thereby indicating the passage of 4 cubic feet 

Sof gas. Now, in the ordinary gas-meter (see 
Fig. 159), instead of four separate vessels, there 
is an outer, cylindrical case, A A, more than 
half filled with water, and a cylindrical drum, 
divided into four compartments, BBBB, re- 
volving in it. The gas enters into the revolv- 
ing inner drum, by a pipe at its center, and 
discharges its gas into the compartment which 
may happen to be over it, causing the compart- 
ment to rise, and the drum to perform a portion 
of a revolution. When the compartment be- 
f I comes entirely filled, its edge, D, is lifted so far 

out of the water that the gas contained in it escapes (passing in the direction 
of the arrows) into the space between the two drums, and is conveyed away 
by a tube not shown in the figure. The revolving drum is connected with 
clock-work, which shows by an index the number of revolutions made, and 
the capacity of the compartments being known, the quantity of the gas pass- 
ing through is accurately determined. The meter described is known as the 
"wet meter," and is the one in most general use. Other arrangements em- 
ployed for measuring gas, dispense with the water, and are termed " dry 
meters."* 

459. Illuminating gas of all kinds, when mixed with air in certain propor- 
tions, forms explosive mixtures ; care, therefore, should be taken, not to enter 
an apartment pervaded with a strong odor of gas, with a light, until a thor- 
ough ventilation has been effected. 

* The gas-meter, when properly constructed, is an exceedingly accurate instrument, 
though frequent differences arise on this subject between gas companies and their custom- 
ers. These discrepancies, occurring between one period of consumption and another, and 
which are always attributed to the meter, arise most frequently from differences in tho 
quality of the gas furnished ; for it is a fact not sufficiently known, that the poorer the 
gas, the faster it will flow through the burners ; and, though the meter has registered 
correctly the volume of gas delivered, it does not follow that the consumer has received 
an equivalent amount of light. A desirable improvement in this direction would be a 
meter registering the time or duration of light, rather than the volume of gas. Until that 
is accomplished, gas companies have no inducement to furnish good gas. The worst ar- 
ticle with which consumers can be satisfied will be more likely to be manufactured, since 
it is the cheapest to produce, and the dearest to sell. 

Question.— What is said of the explosive compounds of illuminating gas? 



CARBON. 307 

460. History . — The fact that a combustible, illuminating gas, is pro- 
duced during the decomposition of coal by heat, was first noticed in 1664, but 
it is only within the present century that any general, practical application of 
this knowledge has been made. Gas was first employed for street illumina- 
tion in London in 1812, and in Paris in 1815. , The majority of householders 
in London were opposed to its introduction into the streets of that city, and 
for many years the advocates of the use of gas for general illumination, en- 
countered a great amount of opposition and ridicule.* 

461. G-as is manufactured from oil, resins, gre ase, etc., by causing them to 
trickle into a retort containing fragments of coke, or bricks heated to redness. 
Decomposition of the oily substances immediately takes place, and the gas 
evolved needs only to be cooled to adapt it to immediate use. 



}~\J 



CHAPTER VII. 

COMBUSTION. 







i 

462. History. — Fire, in the opinion of the ancients, was 
one of the four elements of nature — earth, air, and water 
being the other three. 

This doctrine was generally received until the middle of the 17 th century 
(1650), when a new theory, accounting for the various phenomena of combus- 
tion, was proposed by Beccher, an eminent German physician and chemist, — 
which was afterward, toward the latter part of the same century, still further 
elaborated and explained by Stahl, also a German physician, and one of the 
most eminent scientific men of his age. This theory, which remained undis- 
puted until after the discovery of oxygen in 1714. was known as the " Phlo- . 

gistic Theory y 

It started with the assumption that there existed in nature a distinct 
substance, or agency, constituting the principle of fire, called Phlogiston 
(from the Greek 6loyt&, to burn). Phlogiston, although never isolated, was 
believed to exist in all combustible bodies, and to constitute a part of their 



* At the present time it is estimated that 6,000,000 tons of coal are annually employed 
in England for the manufacture of gas, and from 60 to 75 millions of dollars are expeudcd 
in its production. In London alone, 500,000 tons of coal are annually used, producing 
five thousand million cubic feet of gas, and yielding an amount of light equal to that which 
would be evolved from the combustion of ten thousand million of tallow candles, of six 
to the pound. 

Questions. — What is said of the history and first introduction of gas ? How is gas 
manufactured from oils and resins ? What was the original supposition concerning fire ? 
What theory succeeded ? Explain the general principles of the phlogistic theory? 



308 INORGANIC CHEMISTRY. 

structure, and its presence in such bodies was supposed to endow them with 
the property of burning. "When a body burned, phlogiston was liberated, and 
the light and heat which accompany combustion were attributed to the rapids 
ity which which the phlogiston passed out. "When a body was wanting in 
phlogiston, or had once lost it, it ceased to be combustible, and was said to be 
dephlogisticated. 

For example, according to this theory, a lighted candle burns because it is 
a compound of candle-matter and phlogiston, which compound, in the action 
of burning, is decomposed, and the phlogiston,, set free 3 appears, in escaping, 
in its natural characFer, as flame. The pure, dephlogisticated candle-matter 
is also liberated, little by little, as the candle burns away, and when collected, 
proves to be water and carbonic acid ; so that, according to the phlogistic 
theory, tallow should be regarded as a compound of fire, with water and car- 
bonic acid. Furthermore,, "a stick of brimstone burns away with a blue 
flame and a suffocating vapor, and the residue of its combustion is sulphurous 
acid. In the language of the phlogistians, brimstone is a compound of two 
things, sulphurous acid and phlogiston ; and when it is suffered to burn, it 
gives out its phlogiston, or flame of fire, and there remains its dephlogisti- 
cated sulphur, or sulphurous acid, in the separated state. Phosphorus, ac- 
cording to the same hypothesis, contains a white, deliquescent acid (§ 405) 
and phlogiston — the two so loosely united as to be kindled or decomposed by 
a little friction, or by a slight elevation of temperature ; when burned, it sheds 
its phlogiston, and the phosphoric acid is reproduced." 

It had been long before observed, that the metals, with the exception of 
gold and silyer, were changed into rusts, or "calx£S," resembling chalk, brick 
dust, or other highly- colored earthy bodies,* when heated to a high tempera- 
ture in the air. "We now know these calxes to be simply oxyds ; but tho 
phlogistians, recognizing the only identity of this alteration of the metals with 
what is undergone by sulphur, phosphorus, or any common combustible when 
it is burnt in the air, explained the change as follows : they said that each 
metal was composed of its own rust, or calx, and phlogiston^ and that when 
it was burned in the fire, it gave out its fiery principle, while its ashes or 
rust remained." Thus, iron was composed of iron-rust and fire ; dephlogisti- 
cate it, that is, burn it to a cinder, and you have rust. 

" Such bodies as wood, coal, and especially charcoal, which give out much 
heat, and leave apparently little dephlogisticated matter when burnt, were 
regarded as substances overcharged with phlogiston, and therefore capable of 
imparting it largely to others. Now, it always was, and still is, desirable to 
transform ores, such as iron rust in the various iron-stones, into metals, such 
as iron ; and it has long been understood that the best way of doing so, con- 
sists in mingling those ores with carbon in some form or other, and heating 
them in a furnace ; a thing but too easily explained by the phlogistic theory, 
for the carbon had only to pour its phlogiston into the ores to convert them 
into metallic natures, solid and bright. In the substance of si]v£jxanjd_gold, 



* Iron-rust (oxyd of iron), oxyd of lead, etc 



COMBUSTION. 309 

however, the phlogiston (fire) was so compacted and inherent, that nothing 
could take it out of them ; and hence they remained fixed in the furnace 
under all ordinary circumstances." 

The phlogiston, once liberated from a metal or combustible, could not, like 
the dephlogisticated matter — the phosphoric, or sulphurous acid, or the iron- 
rust — be caught and measured. In the opinion of the ancients, it ascended at 
once into a boundless space of pure fire, called the "empyrean," which was 
supposed to inclose the air as the air inclosed the earth ; but according to the 
phlogistiaus, it was no sooner liberated from a combustible, than it passed 
into combination with the surrounding atmosphere. It could not, in their 
opinion, b°, emancipated from its union with one body, unless another was 
ready to take it without delay, and the appearance called fire, was the almost 
instantaneous glance of phlogiston in its passage from one engagement to an- 
other. Hence the necessity of the presence of air to the continuance of com- 
bustion ; and hence Priestley, when he discovered oxygen, supposed it to be 
common air deprived of phlogiston ; since it did not burn of itself, but power- 
fully supported combustion, by reason of its supposed attraction for the phlo- 
giston contained in combustibles. He therefore called it dephlogisticated air. 

Although the phlogistic theory ingeniously explained a great variety of 
phenomena, there were certain circumstances connected with combustion 
which could not well be accounted for. Thus it was observed that certain 
metals were heavier after heating than before : ten grains or ounces of lead^ 
weigh more than ten after having been burnt to calx.; and ten_punces of 
^iroa- increase in weight by conversion into rust ; — in other words, the metals 
"lead and iron, supposed to be compound bodies, gave off by heating, one of 
their ingredients, phlogiston, and were thereby converted into elements ; and 
yet the product — the calx — was heavier than the original metal ; whereas, if 
phlogiston was really a material substance, and had escaped from the lead or 
the iron, the products, after heating, ought to have weighed less. This diffi- 
culty was explained by assuming that phlogiston, alone of all substances, was 
endowed with the specific property nf lighiaaasSf nr l^xdiyp^n that it buoyed 
up, or made lighter, every body with which it combined. " This singular 
evasion of the question of weight only introduced another perplexity ; but the 
good old chemists were equal to the emergency. If the calx or rust of lead, 
or of any other metal, became lighter, in common balance-weight, by combin- 
ing with phlogiston — that agent of positive levity — how was it that it also be- 
came specifically heavier ? The calx was comparatively a light stone ; but 
the lead into which it was converted by union with light phlogiston, was a 
comparatively heavy metal ; a cubic inch of the metal being twice as heavy 
as a cubic inch of the stone. If the particles of an ounce of calx had buoys 
of fire attached to them, so as at once to change them into particles of lead, 
and to make them lighter in the aggregate, how should such enlarged and 
lightened particles produce a metal of so much greater a specific gravity than 
the unphlogisticated rust ?" To this it was replied, " that the phlogisticated 
particles of calx were not enjarged^but only Jightened ; the fiery particles 
were not stuck on to the calx ones like so many vesicles ; but they pene- 



310 INORGANIC CHEMISTRY. 

trated them, and then compressed them, so that a greater number of the fire- 
pierced earthy particles (thereby rendered metallic) packed into the same 
space, and therefore the metal was specifically heavier, though absolutely 
lighter, than the calx from which it was made."* — Brewster. 

4G3. Such is a brief outline of the celebrated phlogistic theory which dur- 
ing the greater part of the last century received the sanction and support of 
all the chemists and scientific men of Europe. The honor of its overthrow 
and the establishment of correct views, belongs to Lavoisier, whose decisive 
experiments were instituted about the year IT 80. 

Ho took a glass, flask, added to it a certain Tmown weight of metallic^ mer* 
cury, filled the flask with oxygen gas (which had been discovered some years 
previously), and hermetically sealed it. The weight of the whole was then 
carefully ascertained. The mercury contained in the flask wa3 then heated 
to about 6 00° F.) at which temperature it entered into combination with tho 
gas, and formed a calx:, or oxyd of mercury. Lavoisier then weighed tho 
flask and contents, and found that it had gained nothing and lost nothing ; 
the phlogiston, therefore, if it had been driven out from the metallic mercury, 
still remained in or incorporated with the flask and its contents. 

The flask being next carefully opened, the air from without was heard to 
rush into it, indicating the existence of a vacuum in its interior. The mer- 
cury, therefore, had not by heating imparted any thing to the gas of the flask, 
but had really abstracted something from it, and when taken out and weighed 
separately, was found to have increased in weight. That this increase in 
weight was due to the abstraction of .oxygen* and to its incorporation with 
the substance of the mercury, he further proved, by decomposing the calx 
(or oxyd) of mercury (formed in the first experiment) into oxygen gas and 
metallic mercury, by heating it in a suitable apparatus to a temperature of 
about 900° F. The two products being carefully collected, their joint weight 
was found to be the same as that of the calx of mercury employed. These 



» " How catholic, elastic, and satisfactory this venerable hypothesis must have been. 
It -was all wrong, indeed, as a substantive doctrine. In one particular it -was a sort of re- 
verse of truth. It is not the calxes (ores and rusts) and acids that are simple ; it is not 
the combustibles and metals that are compound; it is exactly the reverse. Sulphur, 
phosphorus, carbon, and the combustibles, on the one hand, with lead, iron, and the 
metals on the other, are elementary ; the respective acids and calxes of these principles 
are the compounds. The phlogistians may, therefore, be said to have perceived the re- 
lation subsisting between these two classes of bodies upside down, like the figures in a 
camera obscura. As to the generic idea of phlogiston, erroneous though it was and is, 
it is extant in science yet ; for it is impossible to see wherein caloric differs from it 
as a scientific conception, although elaborated with immensely greater precision, except 
that caloric is the matter of heat, while phlogiston is the matter of fire. Both phlogiston 
and caloric are substances which have no existence whatever in the external world ; they 
have both been convenient, though fictitious representatives of natural realities, and they 
have both been eminently useful in standing for certain phenomena in their several days, 
but the latter creation of the materializing tendency of unripe science is not a whit better 
in essence than the former." — Sib David Behwstek. 

Questions, — Who overthrew the phlogistic theory? By what experiments was ita 
falsity demonstrated ? 



COMBUSTION. 311 

experiments, therefore, proved unmistakably that the calx, or red rust of 
mercury, was a compound of oxygen and mercury, and not an element, as 
had long been supposed ; and that metallic mercury was not a compound of 
its own calx and the positively light phlogiston, but the real element. 

Lavoisier also burned phosphorus in a jar of oxygen, and observed that 
much of the, gas jhaappeared, and that the phosphorus gained in weight; and 
that the increase of the one was in the exact ratio of the decrease of the 
other. Xron wire, also,- burned. in-oxygen, gave a result equal to the weight 
of the wire employed, plus the weight of the oxygen that had disappeared. 

Observing also that the results of combustion in atmospheric air were the 
same in degree as those in pure oxygen, he next investigated the nature of 
air, and found that it consisted in part, of oxygen which supported and occa- 
sioned combustion, and of another gas which possessed properties entirely op- 
posite, and which we now know to be nitrogen. 

The results of the experiments of Lavoisier, therefore, demonstrated that 
there was no such substance as phlogiston, or the matter of fire ; and that 
when a body, compound or elementary, was burned^ it did not give off imag- 
inary buoyant phlog stop, but took in real weighty oxygen. 

Lavoisier commenced his investigations in 17 72, and fully announced them 
in 1784. Eor eleven years he encountered thlTopposition of the whole scien- 
tific world, with but a single supporter — Laplace, the astronomer. Gradu- 
ally, however, the new doctrines gained ground, and before the close of the 
18th century were generally received.* 

From this point discovery rapidly succeeded discovery, until it became at 
last understood that oxygen was not only the great agent in combustion, but 
that the respiration of all animals, the processes of vegetation, and the growth, 
sustenance, and decay of all organic beings were dependent upon it as a con- 
stituent of the atmosphere. The true idea of a chemical element was then 
first arrived at, — affinity or chemical attraction was recognized as an inde- 
pendent force, and the nomenclature of chemistry at present in use was es- 
tablished. In short, the whole science of modern chemistry may be said to 
date its origin from the epoch of the labors and investigations of Lavoisier, f 



* The two great chemists of that day in England, Cavendish and Priestley, never, how- 
ever, abandoned the doctrines of phlogiston. The former, when it became evident that 
the new theory of chemistry had won the day, gave up the science in disgust ; the latter, 
becoming involved in theological difficulties, emigrated to Pennsylvania, where he after- 
ward died — maintaining in his correspondence to the last, a defence of his favorite theory. 

t Lavoisieb. — No attempt to sketch the history of chemistry can be considered com- 
plete without some notice of the life of this celebrated man. He was the son of a rich 
merchant of Paris, and was born in 1743. He early devoted himself to the study of chem- 
istry, as it was then understood, was made a member of the French Academy at the 
age of 25, and was put at the head of the national powder and saltpeter works at 33. Hi3 
great investigations on combustion, the composition of water, atmospheric air, etc., were 
carried on during the years 1772-83, during which period he filled the office of a receiver, 
or " farmer-general" of the public revenues. In 1790 he was a prominent member of the 
famous commission which originated the French system of weights and measures, now 
generally recognized as the true standard by most scientific men. His labors in other de- 
partments of science were also numerous and important. In the common course of 



312 INORGANIC CHEMISTRY. 

/■ . 

464. Combustion, in the strict chemical acceptation of 
the term, is a chemical process in which at least two ele- 
ments enter into combination, producing heat and a new 
compound. 

Combustion, in the ordinary sense, is the rapid chemical 
union of oxygen with a combustible body, attended with 
an evolution of light and heat. 

Every species of combustion with which we are familiarly acquainted is 
simply a process of oxydation ; but combustion may occur without the pres- 
ence of oxygen, or in oxygen without the sensible evolution of either heat or 
light. For example, when antimony in powder or copper in the form of thin 
leaf is presented to chlorine, a combination is instantly effected between these 
bodies — a chloride of copper or antimony being produced, with an evolution 
of vivid light and heat ; and on the other hand, the decay of wood, or the rust 
of metals in air — changes effected by union of these substances with oxygen 
— are true examples of combustion — heat and a new compound being pro- 
duced without the evolution of light. 

465. All bodies may, with reference to combustion, be arranged under one 
of three classes, viz., supporters of combustion, combustibles, and burnt bodies... 

Supporters of Combustion are those bodies which, like oxygen, 
allow other substances to burn in them freely, but which can not themselves, 
in ordinary language, be set on fire. It is usual to reckon five supporters 
of combustion, viz., oxygen, chlorine, iodine, bromine and fluorine. 

Combustibles are bodies which, like charcoal, actually burn when 
sufficiently heated in the presence of a free supporter of combustion. 

Burnt bodies are those which will neither burn themselves nor sup- 
port the combustion of others. They may be made red hot, but do not burn ; 
sand, iron-rust, and earthy bodies are examples of this kind. They are for 
the most part compounds that have at some time or other been produced 
by combustion ; or in other words, they are bodies which have been already 
burned, and are no longer fitted to undergo this change. Chemists further 



events, it might have been expected that the latter years of his life would have been 
passed amid the admiration and reverence which naturally wait upon the originator of a 
new system of acknowledged truths. Such, however, was not his fate. He was arrested 
during the "reign of terror," and thrown into prison, on the wretched charge of having, 
in his capacity of a public officer, authorized the adulteration of the tobacco of the Re- 
public. When brought before the revolutionary tribunal, he asked for a respite of a 
few days, in order to complete some researches, the results of which, he said, were im- 
portant for the interests of humanity. The reply of the judge was, that the Republic 
wanted no scientific men, and forthwith condemned him to the guillotine, to which he 
was dragged the next day, May 8th, 1794, in the 52d year of his age. 

Questions. — Define combustion. Is oxygen necessary for combustion? Into what 
three classes may all bodies be divided in respect to combustion ? What are supporters 
of combustion ? What are combustibles ? What are burnt bodies ? 



J 



COMBUSTION. 313 

distinguish and classify burnt bodies under the names of acids, alkalies^ oxyds, 
salts^etc. — Miller. 

466. Combustion and Explosion . — Explosion in most, and 
perhaps all cases, is a species of combustion, differing from ordinary combus- 
tion simply in the rapidity of action ; thus in combustion, the combustible 
and the supporter of combustion are brought together by degrees, as in tho 
flame of a candle ; but in an explosion the whole action occurs at once. 

467. The origin of the heat which accompanies combustion has not been 
satisfactorily accounted for^C Every change in the state of a body we kuow 
is accompanied by a change in temperature ; but why the union of carbon 
with oxygen to form a gas, or oxygen with hydrogen to form a vapor, should 
produce a heat sufficient to melt -the most refractory substances, still remains 
unexplained. 

468. In all ordinary cases of combustion, the heafc_ 
evolved does not depend upon the combustible, but upon 
the amount of oxygen that enters into combination ; or 
in other words, that combustible will evolve the greatest 
quantity of heat which is capable, with a given weight, 
of combining with the most oxygen. 

For example, ajx>und of hydrogen in burning consumes or unites with 8 
pounds of oxygen; while a pound of carbon unites with but~2~2-3 pounds 
of oxygen. A given weight of hydrogen"hT"burning will produce, therefore, 
three times as much heat as the same weight of carbon. 

469. The quantity of heat which a combustible body 
evolves in combining with oxygen, is the same, whether 
the combustion takes place slowly or quickly, provided 
only that the relative quantities of the combining bodies 
are the same in both instances. 

Thus, as much heat is given out in the decay (slow combustion) of a given 
quantity of wood in the air, as in its quick combustion in a furnace ; but in 
the former case, the heat is much less intense, and often becomes insensible, 
because, during the long time occupied in the combination with oxygen, the 
greater part of it i3 carried away by conduction. 

The temperature required to induce combustion, or the combination of any 
substance with oxygen, is different not only for different substances, but even 
for the same substance, according as the combustion is to take place rapidly 
or slowly. Thus phosphorus combines slowly with oxygen, or exhibits slow 
combustion, at 71° F., but does not enter into rapid combustion till raised to 

Questions. — What is the difference between combustion and explosion? What is the 
origin of the heat evolved in combustion ? To what is the heat evolved by the combus- 
tion of a body proportioned ? Illustrate this principle. Is the quantity of heat increased 
by the rapidity of the combustion ? Illustrate this. Is the temperature at which com- 
bustion occurs constant for the same substance ? What are examples of slow combustion ? 

14 



314 



INORGANIC CHEMISTRY. 





140° F. Tallow thrown upon an iron-plate not visibly red-hot, melts and 
Fig. 160. undergoes oxydation, diffusing a pale, lambent flame, only visible 
in the dark. "When a coil of thin platinum wire is first heated 
to redness, and suspended in a glass containing a few drops of 
ether or alcohol (see Fig. 160), the vapors of these substances, 
mixed with air, oxydate upon the hot metallic surface, and sus- 
tain the wire at a red heat, so long as the supply of mixed vapor 
and air is kept up, without the occurrence of combustion with 
flame. The product of the oxydation thus effected, is a pungent, 
irritating vapor, which affects the nose and eyes unpleasantly. 
This experiment may be modified by suspending a coil of thin 
platinum wire, or a ball of spongy platinum, over the wick of Fig. 161. 
a spirit-lamp, supplied with alcoholic ether, (see Fig. 161); on 
ighting the lamp, and then blowing it out as soon as the 
metal appears red-hot, slow combustion of the spirit vapor 
supplied by the capillary action of the wick, will take place, 
and the platinum will continue to glow for hours. 

470. In combustion, no loss whatever of 
ponderable matter occurs — nothing is annihil- 
ated ; but the products of combustion, when 
collected and weighed, always exceed the weight of the 
original substance burned, by an amount equal to the 
weight of the oxygen absorbed during combustion. 

The most simple illustrations of this fact arc obtained in the combustion of 
those bodies which afford a solid residue. Thus, when two _grains of phos- 
phorus are burned in a measured volume of oxygen gas, they are found con- 
verted, after combustion, into a white powder (phosphoric acid), which weighs 
4-£ grains, or the phosphorus acquires 2^ grains ; at the same time, 7-f- cubic 
inches of oxygen disappear, which weigh exactly 2£ grains. — Graham. 

471. The constituents of all ordinary combustible substances — wood, coal, 
oils, fats, etc. — which give to them their value as fuel, are carbon and hydro- 
gen. These substances also contain some oxygen ; but this^IemenTa)ntrIb^ 
utes nothing whatever to their value as fuel, and the larger the proportion of 
oxygen in a combustible, the less adapted is it for fuel. 

472. Products of Combustion. — When combustion takes place 
with a free supply of air, oxygen unites with the carbon of the fuel to form 
carbonic acid, and with the hydrogen to form vapor of water. These products 
being volatile, rise in the atmosphere, and disappear, forming part of the aerial 
column that ascends from a burning body. 

473. The activity of combustion is greatly increased by increasing jhe nurn- 



Questioxs. — Is any matter lost during combustion? How may this be illustrated? 
Wbat are tbe valuable constituents of ordinary combustibles ? What influence has oxy- 
gen as a constituent of fuel ? What are the ordinary products of combustion ? How may 
the activity of combustion be increased ? 



Hfc 



COMBUSTION. 315 

ber of particles of oxygen which are brought in a given time in contact with 
the combustible, and by carrying away the gaseous products of combustion, 
which are no longer capable either of burning or supporting combustion, and 
which, if allowed to accumulate, would cut off the supply of fresh pxygen. 
Hence the benefit of blowing a fire, or forcing a stream of fresh air "upon it, 
from a bellows, in order to revive it, or increase its intensity. The influence 
of a long chimney, in producing a powerful heat in a furnace at its base, by 
increasing the draft, is similar; while the effects of diminishing the - 'supply of 
air, by closing the damper, or shutting the door of the ash-pit, is seen in the 
diminished temperature, and reduced consumption of fuel which occurs under 
snch circumstances. — Miller. 

474. The wejgh^ftheair required for the combustion of fuel far exceeds 
that of the fuel itself; and aslhlTspace occupied by a given weight of air is 
much greater than that of an equal weight of fuel, the bulk of the air em- 
ployed to effect combustion is immense. For example, it requires 1T45 
pounds of air to consume 1 pound of pure charcoal ; and as 1 pound of 
air occupies about 13 cubic feet of space, the pound of charcoal will require 
for its combustion at least 150 cubic feet of air. As fuel is burned, however, 
a much larger quantity is employed ; thus, anthracite coal requires theoreti- 
cally 136 cubic feet per pound, but in practice, under steam boilers, 276 cubic 
feet are necessary. 

The amount of heat which a pound of pure charcoal is capable of producing, 
through its union with oxygen in the process of combustion, is sufficient to 
convert 13 pounds of water at 60° F. into steam at 212° F. The ingenuity 
of man can not generate from the combustion of a pound of coal a greater 
amount of heat than this, or when generated, compel it to evaporate a greater 
quantity of water. 

The quantity of heat which is obtained from fuel in practical operations, 
falls very far short of its theoretical value. In some of the Cornish steam- 
engines, of England, which are the best in the world, it is stated that the ut- 
most theoretical quantity has been rendered available ; but this statement is 
doubtful. Under ordinary steam-boilers not more than two thirds of the 
available heat is ever utilized, and in a majority of cases the proportion does 
not probably exceed one half. 

The reason of this loss of heat in practice, is due mainly to two causes, viz., 
the heated air escapes up the chimney before it has surrendered to the boiler 
or heating apparatus, the full amount of heat it is capable of relinquishing ; 
and, secondly, through want of a perfect combustion, the full amount of heat 
is not evolved from the fuel. The remedy for the first difficulty is to bo 
sought for in improved mechanical arrangements of boiler and furnace ; the 

Questions. — How is it benefited by blowing it ? Why is the temperature and con- 
sumption of fuel reduced by closing the draft? What is said of the amount of air re- 
quired to produce combustion ? How much air is absolutely required to burn a pound of 
charcoal '? How much heat will a pound of charcoal in burning evolve ? Is the largest 
possible amount of heat from fuel ever wholly utilized ? Why is it in practice that wa 
fail to utilize the full amount of heat derivable from fuel. 



316 INOKGANIC CHEMISTRY. 

remedy for the second pertains to chemistry, and is to be found in perfecting 
the supply of air. When the supply of air is insufficient, carbonic oxyd be- 
comes in great part the resulting product of combustion, instead of carbonic 
acid ; but for the formation of the first-named gas, only one half the quantity 
of oxygen is required as for the production of carbonic acid, so that coal may 
be dissipated in vapor, and may be apparently wholly consumed by one half 
the amount of air that is usually required in an open fire, under circumstances 
where the full amount of heat is given out. In such cases a pound of char- 
coal, instead of emitting heat enough to convert 13 lbs. of water into steam, 
will only give out one fifth of the heat, and will therefore convert but little 
more than 1\ lbs. of water into steam.* That so great an amount of loss as 
this is ever practically experienced, is not probable ; but in all furnaces of 
ordinary construction, the waste of fuel from this source is very great. Owing 
to the fact that carbonic oxyd is a colorless gas, and as the operations of the 
furnace appear to go on uninterruptedly, the loss of heat occasioned in this 
manner is very apt to remain unsuspected. 

By admitting, in a proper manner, an adequate supply of air, all the car- 
bon in burning is converted into carbonic acid, and the maximum of heat 
capable of being evolved from the combustion is generated. 

475. Light of Combustion — The light emitted by burn- 
ing bodies is a direct consequence of the heat evolved in the 
process of combustion. All solids and liquids (as melted 
metals), when elevated to a sufficiently high temperature, 
(977° F.), become luminous. 

The color of the light emitted from an ignited substance, depends upon the 
degree of temperature to which it has been elevated. As the temperature 
rises, the colored rays appear in the order of their refrangibility ; first red, 
then orange, yellow, green, blue, indigo, and violet are emitted in succession. 
At about 2100° P., all these colors are produced, and from their admixture, 
white light results, and the ignited body is then said to be " white-hot." 

In all luminous flames, the light is emitted from solid 
particles highly ignited. 

A flame containing no such particles emits but a feeble light, even if its 
temperature is the highest possible. Por example, the flame produced by 
burning a mingled jet of oxygen and hydrogen, although one of the most in- 



* The great loss of heat involved in the production of carbonic oxyd, is due not merely 
to the fact that carbonic oxyd requires less oxygen for its formation than carbonic acid, 
but the former gas occupies twice the bulk of the latter, and, consequently, renders latent 
a greater amount of heat. 

Questions. — Under what circumstances will fuel be burned to the best advantage? 
Upon what does the light which accompanies combustion depend ? What relation is there 
between the light of an ignited substance and its temperature ? What is flame ? Upon 
what does the luminosity of flame depend ? Illustrate this. 



COMBUSTION. 317 

tense sources of heat at our command, is so little luminous as to be barely 
visible in clear day -light ; if, however, we introduce into it a solid body, like 
lime, the light becomes so augmented that the eye can scarcely support it. 
"When phosphorus is burned in oxygen, the light is most dazzling, but when 
burned in chlorine, it is extremely feeble ; the reason for the difference in 
these two cases is, that in the first instance the product of combustion is 
solid, n on- volatile phosphoric acid, the particles of which, becoming highly 
heated by the combustion, are highly luminous ; in the second case, the pro- 
duct of combustion is a gas, and the heat which its particles acquire in com- 
bustion not being sufficient to render them luminous, little or no light is 
evolved. ^-f- — 

476. Materials for Illumination.— The materials or- 
dinarily employed for effecting artificial illumination, are 
solid or liquid compounds of carbon and hydrogen — coal, 
oils, tallow, etc. — which are generically termed hydrocar- 
bons. 

By heat we decompose them into gaseous compounds of carbon and hydro- 
gen, and in this state only are they available for purposes of illumination. In 
the combustion of these two elements in the flame of a candle, the oxygen of 
the air combines with both, but by reason of a superior affinity, it unites first 
with the hydrogen to form vapor of water, producing, thereby, a most intense 
heat, but an almost imperceptible light. The hydrogen, in combining with 
oxygen, abandons the carbon, which, being thus set free in the form of min- 
ute solid particles in the midst of the heated space, becomes white-hot, and 
imparts luminosity to the flame. The moment, however, the incandescent, 
floating carbon comes to the edge of the flame, it finds the oxygen of the air, 
unites with it, and becomes converted into invisible gas — carbonic acid — 
while its place is immediately occupied by another particle of solid carbon. 

Between the flame of a candle and the flame of gas-light there is no dif- 
ference ; in the case of the candle, however, the gas is generated and burned 
at the same time and place — the heat that produces it serving also to inflame 
it. In the case of a gas-light, on the contrary, the inflammable gas is dis- 
tilled by heat from the illuminating substances in close vessels in one place, 
and conveyed by pipes to be burned at a place more or less distant where the 
illumination is required. 

The fact that the combustion of a candle generates gas of the same nature 
as that produced in ordinary gas manufacture, may be demonstrated by intro* 
ducing one end of a small tube of glass, p, Fig. 162, into the interior of tho 
flame of a large candle, when a portion of the inflammable gas existing there 
may bo drawn off and ignited at the upper extremity of the tube. 

Questions. — What are the materials ordinarily used for artificial illumination? What 
are hydrocarbons ? In what condition only are they available for illuminating purposes ? 
What takes place during their combustion ? What difference is there between the flame 
of a gas-burner and that of a candle ? How may the production of inflammable gas in a 
candle be demonstrated ? 



318 



INORGANIC CHEMISTRY, 



Fig. 162. 




fore it could inflame. 



The existence of solid particles in every illuminating 
flame may be also demonstrated by introducing a cold 
body into the flame, which so interrupts the progress 
of combustion that the solid particles are no longer 
consumed, but are deposited as soot. When we say 
a lamp smokes, we mean that the carbon contained 
in the flame is passing off in an unconsumed state. 

4:11. Combustion of a Candle. — A candle 
is an ingenious contrivance for supplying flame with 
as much melted fat as it can consume without smok- 
ing. It is easy to conceive that it would by no means 
be an impossibility to ignite a stick of wax or tallow 
by itself; it would, however, be a matter of difficulty, 
inasmuch as the material would melt away long be- 
Supposing, nevertheless, it could be ignited, then a 
larger amount of combustible would be on fire than the air could consume, 
and a large, thick, smoky flame would result. By the use of a wick, this dif- 
ficulty is avoided. 

"When the end of the wick which protrudes from the center of the candle 
is ignited, it radiates sufficient heat downward to melt a portion of the ma- 
terial of the candle, and form a hollow cup filled with liquid combustible 
around the wick-fibers. The spaces between the fibers of the wick, acting 
like a series of small tubes, convey the fluid fat by capillary attraction up to 
the flame, where it is decomposed into gaseous compounds of hydrogen and 
carbon. 

478. Structure of Flame . — The flame of every lamp or candle 
consists of three distinct portions, or rather, cones concentric with one an- 
other. The innermost cone, a, Fig. 163, is formed entirely of 
combustible gases, produced by the decomposition of the illu- 
minating material. This is at a temperature below redness, 
and is consequently non-luminous. Around this is the lumin- 
ous cone (&), the flame proper, where the hydrogen is uniting 
with the oxygen of the air, and the particles of carbon not 
having yet done so, are floating about in an incandescent state 
and radiating light. Beyond the second cone is another film, 
or casing (c), where the oxygen of the air unites with the car- 
bon, and in a properly adjusted flame is entirely consumed. 
In the flame of a gas-jet the same parts may be also recognized. 
At the base of every flame a pale blue line of light may be ob- 
served; at this point, the supply of oxygen from the air is 
insufficient to completely and simultaneously consume both the 
hydrogen and the carbon supplied from the interior of the flame, and there 
being no solid carbon eliminated, there is consequently but a feeble light. 

Questions. — How may the presence of solid particles in a flame be demonstrated? 
When we say a lamp smokes, what is understood ? What is the necessity of the wick in. 
a candle ? Describe the structure of the flame of a candle. 



Fig. 163. 





COMBUSTION. 319 

The portion of wick within the interior of a candle flame is charred and 
blackened by the heat, but not consumed, owing to the fact that the burning 
envelop which surrounds it effectually cuts off all access of air, and thus 
prevents combustion. For the same reason, also, the interior cone of com- 
bustible gases, in every luminous flame, remains uuignited. 

The tapering and conical form which flames assume, is due to the ascending 
currents of rarefied air which are produced in the atmosphere by the heat 
attendant on the combustion. 

479. That the combustion of a candle is superficial, and that the flame is a 
film of white-hot vapor, inclosing an interior portion which can not burn for 
want of oxygen, may be demonstrated by bringing clown upon the flame a 
piece of thin glass, so as to make a transverse section of the flame ; we shall 
then observe a ring of light surrounding the dark interior part of the flame. 
This experiment may bo still better performed by means of a piece of fine 

Fig. 164. wire gauze. "When this is brought down upon the flame 
of a large and steadilv burning candle, the flame will be 
cut off where it touches the gauze, and the exterior lumin- 
ous circle will be well defined. (See Fig. 164.) 

That no combustion can go on in the center of flame, 
may be shown in various ways ; as for example, if we ig- 
nite a small quantity of strong alcohol in a saucer, and 
place a rod of white wood across it for a few seconds (sea 
Fig. 165), it will be found on removing the stick, that it is 
burned or blackened at only two points, viz., where the 
flame was in contact with the air. The same thing may 
a'so be shown by holding a match stick for a few seconds 
across the middle of the flame of a spirit-lamp with a large 
wick. If a fragment of phosphorus be placed in a small 
circular spoon, ignited, and then introduced into the mid- 
dle of a large flame, it will be extinguished, but will be re- 
kindled the moment that the spoon is withdrawn from the flame. 

480. In order that a flame should exist, a very high temperature is es- 
sential. This is particularly the case with the flames produced by the com- 
bustion of the hydrocarbons ; and if in any manner the temperature of a 
flame is reduced beyond a certain limit, it is immediately extinguished. 
Thus, if a stout copper wire be introduced into a flame, it will be observed 
that a dark space is produced around it ; a second wire cools the flame still 
further ; and a small flame may be completely extinguished by the cooling 
effect produced by bringing down a coil of wire upon it. If a fine wire-gauzo 
be brought over a flame, the inflammable gases will bo so far cooled by pass- 
ing through its meshes (their heat being conducted off), that they no longer 
continue in a state of inflammation. (See Fig. 164.) If the meshes are very 

Questions. — Why is not the -wick of a candle consumed? Why are flames tapering 
and conical? What experiments prove that the flame of a candle is superficial? What 
that no combustion goes on iu the interior of the flame ? What is essential to the exist- 
once of flame? Illustrate this ? Why can not a flame pass through a wire-gauze ? 




320 



INORGANIC CHEMISTRY. 



Fig. 1GG. 




fine, the conducting power of the metal is sufficient to 
cool the flame below the point of ignition, even though the 
wire itself may be red-hot. The inflammable vapor which 
passes through the gauze may, however, again be kindled 
by the direct application of flame. 

These experiments are well illustrated with a jet of 
gas issuing under low pressure. If the gauze be held over 



applied above, it 
not pass through 
we place 



the jet before it is lighted, and a flame 
will take fire there, but the flame will 
to the gas below. (See Fig. 167.) If 



Fig. 167. 



Fig. 163. 



a piece of camphor on the center of the wire- 
gauze, and ap*ply a flame below, the cam- 





Ftg. 169. 



phor will melt and pass through the meshes, 

but will burn only on the under side. (See 

Fig. 168.) 

481. Safety-Lamp. — These facte, discovered 

Sir Humphrey Davy, were beautifully applied by him 
the construction of the "Safety-Lamp," which allows the 
miner to work in safety in an atmosphere pervaded with an 
explosive mixture of light carburetted hydrogen (fire-damp, 
see § 452). It consists merely of a common oil-lamp, the 
flame of which is completely inclosed within a cylinder of wire- 
gauze. (See Fig. 169.) This completely arrests the passage 
of the flame ; so that, although the lamp be introduced into an 
explosive mixture, the flame will not pass through the gauze 
to ignite it. 

482. Requisites for the Production of Arti- 
ficial Light. — The essential requisites for the 
successful production of artificial light by the 
combustion of the hydrocarbons, are, 1st. That 
there should be a free .supply of air ; and, 2d. 
That the products of combustion should be freely con- 
ducted off. 

These two facts may be illustrated by placing a glass cylinder over a lighted 
candle, in such a way as to cut off its connection with air /row below ; the 
flame, in this case, will be extinguished for want of a free supply of air. If 
the cylinder be now closed at the top, but held over the candle in such a way 
that the air can gain admittance from below, the flame will also be extin- 
guished, since the burnt gases, the products of combustion, are unable to 
escape, and by their accumulation, prevent combustion. If the cylinder be 




Questions — To what invention has this principle been applied ? Describe the safety- 
lamp. What are the essential requisites for the production of artificial light? How may 
these be illustrated ? 



COMBUSTION. 



321 



Fig. 170. 




placed in such a way that the air can gain free 
admittance below, and escape freely at the top, 
bearing with it the products of combustion (see 
Fig. 170), the candle will not only continue to 
burn uninterruptedly, but its combustion will be 
more perfect, than when it is allowed to burn 
openly in the air. The reasou of this is, that the 
ascent of the air, heated by the combustion, 
creates a rapid current of fresh air from below up 
through the cylinder — thus supplying more oxy- 
gen within a given time and space, which occa- 
sions more perfect combustion, and a stronger 
illuminating flame. Hence the benefit of sur- 
rounding a lamp-flame with a glass chimney, open at the bottom and top. 

If too much air be supplied to a flame, the inflammable gases burn with a 
blue and feeble light, an effect which may be seen by blowing upon a com- 
mon gas-flame, or by watching the exposed gas-lights of shops upon a windy 
night. In these cases, the gas becomes immediately mixed with the oxygen 
of the air, which burns up the solid particles of carbon before they are suf- 
ficiently heated to afford light. 

The necessity of air for the support of flame, is also strikingly shown by the 
fact, that it is impossible to light a lamp or candle with a match, so long as 
the sulphur on the end of it is burning freely ; since the sulphurous vapor 
abstracts the oxygen from the air around the wick, in order to form sulphur- 
ous acid. 

483. Argand Lamps. — In an ordinary 
lamp or candle-flame, the combustion goes on only 
at those points where the air has free access, viz., 
upon the outside of the flame, as is indicated by 
the existence of a dark central portion. If, how- 
ever, air be introduced into the interior of the 
flame, combustion is effected both at the center 
and at the circumference, and the light is increased. 
This arrangement is practically carried out in 
those lamps which are fitted with hollow or cir- 
cular wicks, and which are known as " Argand" 
lamps, from their inventor. In these, a current of 
air rushes up, through the hollow wick, into tho 
center of the flame, as shown by the central ar- 
rows, Fig. 171, causing it to burn in the form of a 
1 J| J || Ym \ hollow ring. Tho combustion is also made moro 

i! powerful, by surrounding the flame with a glass 

chimney, which is usually made conical, or is 



Fig. 171. 




Questions. — What Is the effect cf admitting too much air to a flame ? What is an 
Argand lamp ? Describe its construction ? 

14* 



322 



INORGANIC CHEMISTRY. 



Fig.. 172. 




caused to contract at a certain height above the burner, so as to form a 
shoulder, A B, in order to deflect the ascending outer current of air, and 
throw it in upon the flame at an angle. In this way the temperature cf the 
separated carbon particles of the flame is enormously increased, and the 
greatest quantity of light is produced, from a given amount of fuel 

The effect of the draft through the interior of the wick, on 
the combustion of the inflammable gases, may bo readily 
made apparent by closing, with a piece of paper, the openings 
in the base of the lamp, through which the air gains admis- 
sion. The flame will immediately become impaired in bril- 
liancy, burning with a red light, and the evolution of much 
smoke. 

In an Argand lamp we are able to burn the poorer and 
cheaper oils (those which contain an excess of carbon) with- 
out the production of smoke ; inasmuch as the greater supply 
of air effects the entire combustion of 
carbon; whereas, in an ordinary lamp, 
by reason of the limited supply of air, 
we can use only the best oils, or those 
which contain a large proportion of hy- 
drogen. Fig. 172 exhibits the external 
construction of an Argand burner, and the direction of 
the currents of air. 

Fig. 1 74. 484. B e r z e 1 i u s Spirit-Lamp . — The 
so-called "Berzelius Spirit-Lamp" (see Fig. 
173), employed in chemical laboratories for_=|j|l§| 
obtaining a degree of heat greater than thatjgKIp 
afforded by an ordinary spirit-lamp, is simplyi 
an Argand lamp, fitted to burn alcohol, and|^, 
supplied with a metallic chimney, in place of " 
one of glass. The standard to which it is attached is provided 
with several rings of various sizes, for sustaining crucibles, por- 
celain dishes, etc., which are to be heated. 

485. The Blow-Pipe . — The principles upon which the 
blow-pipe operates are essentially the same as those involved in 
the construction of the Argand lamp: a jet of air or oxygen is 
thrown into the interior of a flame, by which the rapidity of com- 
bustion is increased, and the heat of the flame powerfully augmented. 
The mouth blow- pipe consists essentially of a bent tube, gener- 
ally of brass, terminating in a fine uniform jet. (See Fig. 174). It 
is usually also constructed with, a chamber, or enlargement of tho 
tube, near its small extremity, which serves to collect the moisture 
which condenses from the breath. When the jet of the blow-pipe 

Questions. — What is the effect of closing the inner draft of this lamp ? How is an Ar» 
gand lamp enabled to burn cheap oil ? What is a Berzelius spirit-lamp ? What is the 
theory of the blow-pipe ? What is the construction of a blow-pipe ? 




COMBUSTI ON. 



323 




is inserted into the flame of a candle, Fig. 1*75. 

and a current of air forced from it, 

the flame loses its luminosity, and is 

projected laterally in the form of a 

beautiful, pointed cone, in which two 

parts are distinctly discernible, viz., a 

small, blue interior cone, a &, and a 

larger exterior cone of a yellowish 

appearance, c. The different parts of 

this flame possess very different properties. 

The blue cone is formed by the admixture of air with the combustible 
gases rising from the wick ; in this part of the flame the combustion is com- 
plete, and the heat greatest. In front of the blue cone is the luminous por- 
tion, consisting of unburnt combustible gases at a high temperature, which 
of course have a*powerful tendency to combine with oxygen. If a fragment 
of some metallic oxyd, such as oxyd of copper, be introduced into this part 
of the flame, the oxyd will be deprived of its oxygen, in consequence of 
the superior affinity of the hot gases for this element, and will bo re- 
duced to a metallic state : hence this portion of the flame of the blow-pipe 
is termed the " reducing flame." At the apex, or extreme point of the outer 
flame, these effects are reversed. Here atmospheric oxygen at a high tem- 
perature exists, and its tendency is to unite with any substance with which 
it may be brought in contact. Hence if a fragment of metal, such as lead, 
tin, copper, etc., be placed at this point, it will quickly become covered with 
oxyd ; and this spot is, therefore, called the " oxydizing flame" of the blow- 
pipe. 

The opposite actions of the different portions of the blow-pipe flame mny 
be illustrated by the effects which they produce upon a piece of flint-glass, 
which contains oxyd of lead, united with silica. In the reducing flame the 
silicate of lead is partially decomposed, and the glass at this point becomes 
black and opaque from the reduction of the oxyd of lead to the metallic 
state ; but by placing the blackened part for a few seconds in the oxydizing 
flame, oxygen is again absorbed by the metal, and the transparency of the 
is restored. — Miller. 



Fig. 176. 





So also if we hold a brightly pol- 
ished cent over the flame of a spirit- 
lamp (see Fig. 176) the parts exposed 
to the exterior of the flame will be- 
come covered with an iridescent 
coating of oxyd, while those over tho 
center of the flame remain bright. 
By moving the coin, after it has be- 
come thoroughly heated, to and fro 
over the flame, a very beautiful play 



Questions. — What is the constitution of the blow-pipe flame? What is the reducing 
and what the oxydizing flame? How may their two actions be illustrated ? 



324 INORGANIC CHEMISTRY. 

of colors will be observed, the metal being alternately converted into oxyd, 
and the oxyd into metal. 

486. Carbon, during the act of combustion, as in an ordinary flame, assumes 
two consecutive phases, viz., while it is evolving heat and light it is a solid, 
but immediately after it becomes a gas. It is this property which renders 
carbon, of all combustible bodies, the most suitable for heating and illuminat- 
ing purposes — questions of cost and convenience being set aside. Phosphorus 
burns in the air with a more brilliant light than carbon — yet this substance 
could not be used as an agent for producing light and heat, since the solid 
products of its combustion remain solid, and being deposited on contiguous 
objects, soon smother the combustible beneath its own ashes. Zinc, when 
highly heated, burns in the air with a brilliant flame, but the products of its 
combustion — white oxyd of zinc — fall about the illuminating center in a min- 
iature shower. The ordinary product of the combustion of carbon, on the 
contrary, is a gas, carbonic acid, which in virtue of its gaseous qualities es- 
capes into the atmosphere, and combustive action remains unimpeded. Had, 
however, the results of its combustion been a permanent solid, " the world 
would have been buried beneath a covering of ashes."* 



CHAPTER VIII. 

THE METALLIC ELEMENTS. 

487. History. — Of the whole number of elementary 
substances included in the class of metals, fully one half 
are so rare, that they are known only to the chemist and 
the mineralogist ; of the remainder, some fourteen or fif- 
teen only admit of any extensive practical applications. 
But eight metals were supposed to be known to the an- 
cients. 

* There can scarcely be conceived a more beautiful balance of powers designed for the 
accomplishment of a specific end, than this fixation of carbon in a pure state, and the 
volatility of its oxygen compounds; yet so familiar has the result become to us — so un- 
noticed by its very perfection — that an effort of chemical reasoning is required to enable 
us to appreciate it The enormous quantity of ponderable, yet invisible carbon removed 
in the draught of our larger fireplaces is, on its first announcement startling ; yet nothing 
admits of more satisfactory proof. Through an average sized iron blast furnace thero 
rushes hourly no less a quantity of atmospheric air than six tons, carrying off fifty-six 
hundredths, or more than half a ton of carbon in the form of carbonic acid. — Faraday. 

Questions.— What two phases does carbon assume in combustion ? Why is it the most 
suitable of all bodies for combustion ? Why could we not use phosphorus as an illuminat- 
ing agent ? What is said of the relative abundance of the metals ? 



THE METALLIC ELEMENTS. 325 

488. Properties . — The metals, a3 a class, are characterized by a pe- 
culiar luster, termed metallic ; a property exhibited in the highest degree by 
burnished steel, and the reflecting surfaces of mercury in glass mirrors. They 
are also possessed of a high degree of opacity, and are good conductors of heat 
and electricity. 

Density . — In density the metals differ greatly ; potassium and sodium 
being lighter than water, while gold and platinum are the most dense of all 
substances, being respectively nineteen and twenty-two times heavier than 
an equal bulk of water. 

Hardness . — Titanium and manganese are the hardest of the metals, 
being harder than steel ; lead may be scratched by the finger-nail ; potassium 
and sodium are as soft as wax ; while mercury, at ordinary temperatures, is 
a liquid. 

' Malleability and Ductility .—The most malleable of the metals 
are gold, silver, copper, tin, cadmium, platinum, lead, zinc, iron, nickel, potas- 
sium, sodium, and frozen mercury — in the order given. These may all be 
hammered out into plates, or even into thin leaves. 

The same metals are likewise ductile, or may be drawn into wires, although 
the ductility of different metals is not always proportional to their malleability. 
The most ductile of the metals are gold, silver, platinum, and iron. 

In the manufacture of gold-thread, by recently improved processes, gold in 
combination with silver is drawn into wire, by forcing it through smooth 
conical holes perforated in rubies — so fine, that a single ounce is made to 
stretch over a length of sixty miles. 

Tenacity . — The tenacity of the metals, or the power which they pos- 
sess of resisting tension without breaking, is determined by ascertaining tho 
weight required to break wires of them having the same diameter. Iron 
appears to possess this property in the greatest, and lead in the least degree. 
A wire of iron IMOOths of an inch in diameter, will sustain a weight of 444 
lbs. ; a wire of copper of the same diameter, 300 lbs. ; of gold, 13*7 ; of 
lead, 24. 

The tenacity of metals, however, varies greatly in the same metal, with its 
purity and the method by which it has been wrought. Eecent experiments, 
made under the direction of the U. S. "War Department, have shown that tho 
cohesive strength of iron is greatly increased by fusing it a number of times 
up to a certain point — its capacity to resist transverse strains being increased 
thereby sixty per cent. The tenacity of iron is closely dependent on its 
density. Thus cast-iron, having a density of 6*900 has a tenacity five times 
less than iron of a density of 1*400. Iron castings of the greatest weight, 



Questions. — What are the leading characteristics of the metals'? What is said of their 
density? Of their hardness ? What metals are the most malleable ? What most duc- 
tile ? What are illustrations of the ductility of the metals ? How is the tenacity of a 
metal determined ? What metals possess this property in the greatest and least degree ? 
How may the cohesive strength of iron he increased ? What connection is there between 
the tenacity of iron and its density ? 



326 INORGANIC CHEMISTRY. 

according to their size, are by far the strongest, and weighing them is a ready 
means of judging comparatively of their strength. 

A corrugated sheet of metal, or one that is doubled into ridges and folds, 
will resist a far greater crushing force than a flat surface. In the case of cop- 
per, the ratio of strength has been proved to be as great as 1 to 9. 

Fusibility . — All the metals admit of being fused by the application 
of heat, but the temperatures at which they liquefy are very various. Mer- 
cury, for example, remains fluid at a temperature as low as — 39° F., while 
platinum, iridium, rhodium, and several others, require the intense heat of 
the voltaic battery or the oxyhydrogen blow-pipe to effect their fusion. 

Welding . — Some metals acquire a pasty or adhesive state before under- 
going complete fusion, in which, if two clean surfaces be presented to each 
other, and strong pressure or hammering be employed, they unite or weld 
together, so as to form one continuous mass. The metals which possess this 
property are iron, platinum, palladium, and the metals of the alkalies. 

Volatility . — At higher temperatures than is required for their fusion, 
all the metals are probably volatile. Seven of the metals are so volatile as 
to admit of distillation from the compounds which contain them. They aro 
mercury, arsenic, tellurium, cadmium, zinc, potassium, and sodium.* 

489. Alloys . — Combinations of the metals with metals are termed Al- 
loys, many of which are most extensively used in the arts, as brass, bronze, 
bell-metal, type-metal, German silver, etc. 

490. Amalgam . — When the metals combine with mercury, the result- 
ing product is called an amalyam. 

It is sometimes questioned whether alloys are true chemical compounds ; 
but the general opinion at the present time is, that they are mixtures of defi- 
nite compounds, with an excess of one or other metal. The evidence in 
favor of this view is, that some definite compounds of the metals occur natu- 
rally ; and when an alloy is formed, the specific gravity of the compound is 
either above or below that of the mean of the metals employed ; the fusing point, 
also, of an alloy is generally much lower than the mean of the metals which 
compose it. This is strikingly shown in an alloy called the "fusible metal," 
which is composed of 8 parts of bismuth, 5 of lead, and 3 of tin, and melts 
at 203° F. — a temperature more than 200° below the melting point of tin, 
the most fusible of its constituents, and 400° below that of lead. Its low fu- 
sibility may be illustrated by melting a quantity of it in a paper crucible. 



* Beams of wood suspended over copper smelting furnaces have been observed to be 
pervaded throughout their entire structure with minute beads of metallic copper — tl:« 
copper having been raised in vapor, and so deposited within the fibers of the wood. Goll 
maybe seen to undergo volatilization in the focus of an intensely powerful burning-glass ; 
and fine wires of the most refractory metals may be dispersed in vapor by transmitting a 
powerful electric discharge through them. — Millek. 



Questions. — What effect has corrugation on the strength of a metal ? What is said of 
the fusibility of the metals ? What is welding ? What metals can be welded ? What is 
Baid of the volatility of the metals ? What are alloys ? What are amalgams ? 



POTASSIUM. 327 

491. All the metals have the property of assuming the crystalline form 
but it is not always easy to place them under circumstances favorable to their 
doing so. Some of them occur in nature, in a crystallized state, particularly 
gold, silver, copper, bismuth, and platinum. 

492. All the metals are capable of uniting with oxygen, but they differ 
greatly in their affinities for this element. The greater number combine with 
it at all temperatures, and arc reduced (deoxydized) with difficulty. Others 
on the contrary, like gold and platinum, can not be made to combine with 
oxygen directly ; and their oxyds are decomposed at a slight increase of 
temperature. 

The metallic oxyds differ greatly in their properties. Some of them pos- 
sess basic characters more or less marked ; others will not combine with either 
acids or alkalies ; while a third class have distinctly acid properties. The 
strong bases are all protoxyds, containing single equivalents of metal and 
oxygen ; the peroxyds are generally neutral, while the metallic acids contain 
the largest quantities of oxygen. 

493. Classification of the Metals. — The metals maybe 
arranged in four classes, viz. : 1. The metals of the alka- 
lies ; 2. The metals of the alkaline earths ; 3. The metals 
of the earths ; 4. The heavy metals, or metals proper. 

The latter class may be again subdivided, according to the affinity of the 
metals contained* in it for oxygen, into two groups — the noble and the com- 
mon metals. The former resist the action of oxygen, like gold, silver, ete. ; 
while the latter, like iron, lead, copper, etc., unite with it readily. 



CHAPTER IX. 

THE METALS OF THE ALKALIES. 

The metals which by oxydation produce alkalies are 
Potassium, Sodium, Lithium, and a hypothetical sub- 
stance, Ammonium, the radical of Ammonia. 

SECTION I. 

POTASSIUM. 

Equivalent, 39-2. Symbol, K (Kalium). Specific gravity, 0'865. 

494. History. — Potassium was discovered by Sir Hum- 
phrey Davy in 1807, who obtained it by decomposing 

Questions. — Do all the metals crystallize ? "What is said of the affinities of the metals 
for oxygen ? What are the characteristics of the metallic oxyds ? How may the metals 
be classified ? What are the noble metals ? When and by whom was potassium discov- 
ered? 



' 



t 

.. 
328 INORGANIC CHEMISTRY. 

.Jiydrate_of potash (KO, HO) by the action of a powerful 
galvanic battery. 

The discovery of potassium marks an era in the progress of chemistry. 
The alkalies and the alkaline earths had long been suspected to be compound 
bodies, but up to this period they had resisted all attempts to decompose 
them. When once, however, potassium had been separated from its com- 
pounds, and potash had been proved to be an oxyd of this metal, the de- 
composition of the other alkalies and earths, and the discovery, in quick suc- 
cession, of sodium, barium, strontium, and calcium, 'followed as a necessary 
consequence. 

495. Distribution • — Potassium is widely diffused in nature, but al- 
ways in combination with other bodies. Many of the minerals which com- 
pose the crystalline rocks, such as feldspar, mica, etc., contain potash united 
with silica — silicate of potash. As these rocks crumble down into soils, 
potash assumes a soluble form, and is gradually taken up by plants, and ac- 
cumulated in their structure. "When plants are burned, the potash thus ab- 
sorbed constitutes a part of their ashes, and from these nearly all our supplies 
of this substance are derived. Potassium also exists in sea- water, as chloride 
of potassium. 

496. Preparation . — The original method of preparing potassium 
through the agency of the galvanic battery is troublesome and expensive, 
and a new method has been devised, which consists essentially in subjecting 
a mixture of finely pulverized charcoal and carbonate of potash in an iron 
retort to an intense heat; decomposition of the alkali ensues, and the potas- 
sium distils over in metallic globules which are collected in a vessel of 

naphtha. 

497. Properties . — When a globule of potassium is freshly cut open, 
it appears as a brilliant, silver-white metal ; but the exposed surface in- 
stantly tarnishes by contact with the air, and in a few minutes becomes cov- 
ered with a white coating of ox}^d (potash). At common temperatures it is 
soft, and may be molded like wax ; at 32° F. it is brittle and crystalline. Its 
attraction for oxygen is so great, that it can only be preserved in a pure state 
in exhausted and sealed glass tubes, or under the surface of some liquid, 
like naphtha, which contains no oxygen. At high temperatures it will re- 
move oxygen from almost all bodies which contain this element, with which 
it is brought in contact. The powerful attraction of potassium for oxygen 
may be illustrated by throwing a small piece of the metal upon the surface 
of water, in which case a part of the water is immediately decomposed — its 
oxygen combining with the potassium to form potasli^lvh'ilst the liberated 
hydrogen, taking fire from the heat evolved, burng^iu connection with a por- 
tion of ths volatilized metal, with a beautiful rose-red flame (see Fig. lit); 

Questions. — What consequences followed the discovery of potassium ? What is 6aid 
of its distribution ? From whence are the chief supplies of potassium and its compounds 
obtained ? How is potassium practically obtained ? What are its properties ? WhM is 
said of its attraction for oxygen ? How may this be illustrated ? 




POTASSIUM. 329 

the potassium at the same time fusing, assumes the p IG# i^ 

spheroidal state (§ 15-4), and moves over the surface of 
the water with great rapidity, finally disappearing with 
an explosive burst of steam, as the globule of melted 
potash, which is formed by oxydation, becomes suffi- 
ciently cool to come in contact with the water. If this 
experiment, which is one of the most beautiful in chemistry, be made on a 
vessel of water reddened with a vegetable color, the alkali produced changes 
this color to blue or green. 

49S. Compounds of Potassium. 

Protoxyd of Potassium, Potash, or Potassa, JUL — 
The only known method of obtaining this oxyd free from water, is by ex- 
posing potassium to dry air, when it oxydates to a fine white powder. -^V J> 
once united with water, no degree of heat is sufficient to expel the water. K^ 

The potash of commerce and of the laboratory is always a hydrate (KO, HO). 
It is prepared by dissolving carbonate of potash in ten or twelve times its 
weight of water, in a clean iron vessel, and adding to the boiling solution a 
quantity of good quick-lime equal in weight to half the carbonate of potash 
used. The lime should be previously slacked, made into a cream with water, 
and added in small portions at a time, so that the liquid may be kept at the 
boiling point. The lime abstracts the carbonic acid from the potash, and 
forms carbonate of lime ; which, being insoluble, is precipitated, leaving hy- 
drate of potash in solution. The clear solution, if properly prepared, will not 
effervesce on the addition of hydrochloric acid, thus showing that all the car- 
bonic acid has been transferred from the potash to the lime. The clear liquor, 
which is known as solution of caustic potash, when drawn off by a syphon from 
the precipitate, and evaporated to dryness,, yields a grayish-white solid, with 
a crystalline fracture — the crude potash of commerce. This, melted and cast 
into sticks, constitutes the caustic or fused potassa of the shops {lapis infer- 
nalis), and is used in this state by the surgeons as a cautery. 

499. Properties , — Hydrate of potash, after fusion, is a Hard, grayish- 
white substance ; very deliquescent, and dissolving freely in water and alco- 
hol. Both in the solid state and in solution, it rapidly absorbs carbonic acid 
from the air, and must therefore be preserved in closely-stopped bottles. 

Hydrate of potash possesses in solution, the properties termed alkaline, in 
the very highest degree. It neutralizes the most powerful acids ; restores the 
blue color to reddened litmus, changes the blue infusion of cabbage into green, 
but in a short time entirely destroys these colors. It has a peculiar odor, 
an acrid and disgusting taste, characteristic of the alkalies, and quickly de- 
stroys both animal and vegetable matters ; for thi3 reason, its solution can 
not bo filtered, except through pounded glass or sand, and is always best clar- 
ified by allowing the impurities to subside, and then decanting off the clear 

Questions How may potash free from water be obtained ? What is the composition 

of commercial potash ? How is it prepared ? What is caustic potassa ? What are ita 
properties ? 



330 INORGANIC CHEMISTRY. 

liquor. Hydrate of potash, when handled, imparts to the fingers a peculiar, 
soapy feel, which is occasioned by a gradual solution of the skin (cuticle). 

The affinities of potassa when heated are so powerful that but few sub- 
stances are capable of resisting its action ; those which contain silica are decom- 
posed by it, and even platinum itself is oxydized by it. With the fats and 
fixed oils it forms soaps, which are true salts, composed of a fatty acid and the 
alkaline base. Its applications also in chemistry and in the arts are almost 
innumerable. 

...500. Potassa is the strongest base known in chemistry; consequently, it 
may be used to effect the decomposition of almost every salt. This may bo 
illustrated by adding a solution ofpotash to a solutiorTof either the sulphates 
of iron (green vitriol) or copper (blue vitriol), in water ; the potash immedi- 
ately unites with the acid, and the insoluble metallic oxyd is precipitated 

Potash is a fatal corrosive. poison. 

501. Carbonate of Potash, K0,C0 2 .— Pearlash.— This 
important salt is obtained almost exclusively from the 
ashes of land plants ; the ashes of marine plants, on the 
contrary, contain soda, and but comparatively little potash. 

In countries where wood is most abundant, as in some parts of the United 
States, Canada, Russia, etc., it is burned exclusively for the sake of its ashes. 
These are collected, placed in large tubs (leach tubs), and treated with water ; 
the water soaking through the ashes, dissolves out the potash salts, together 
with various other soluble mineral substances, and is converted into ley ; this 
when evaporated to dryness, yields an impure carbonate of potash, which is 
sold in commerce in immense quantities, under the names of pot and pearl- 
ashes. 

The weight of ashes furnished by different plants varies in different species 
and soils. Herbaceous plants yield more than woody ones; and the leaves, 
bark, and young shoots are the parts which furnish the greatest quantity of 
alkali. Potash does not exist in plants in the form of carbonate, but is accu- 
mulated in their substance in combination with certain organic acids. Thus, 
potash in the vine is combined with tartaric acid, and in the sorrel with ox- 
alic acid. When plants are burned, these acids are destroyed, and the potash, 
uniting with carbonic acid formed during the combustion, is obtained in the 
form of a carbonate. 

Carbonate of potash has strong alkaline properties, and dissolves in about 
twice its weight of water. 

502. Bi-Carbonate of Potash, K , 2 C 2 is a compound con- 
taining double the quantity of carbonic acid that ordinary potash does ; it is 



Questions. — "What gives to potash its peculiar feeling? What is snid of its affinities 
and uses ? What of its basic properties ? From -what source is carbonate of potash ob- 
tained ? What is the process of preparing it ? Under what name does it occur in com- 
merce ? What is said of the amount of ash yielded by plants ? In what state does potash 
exist in plants ? What is bi-carbonate of potash ? 



POTASSIUM. 331 

very generally known under the name of "saleratus," but this term is often 
applied to designate any purified carbonate of potash. 

503. JV i t r a t e of Potash, K , N 5 . — Saltpeter, Niter.— This salt 
occurs somewhat abundantly as a natural product. The chief sources of its 
supply are certain districts of the ■East-Indies, where it is found disseminated 
through the soil, or as an efflorescence. upon the surface. It is obtained in a 
separate state by treating the earth with watery and allowing the solution to 
crystallize. It is supposed to be produced by the decomposition of organic 
matters containing nitrogen in soils containing potash and lime. 

In Europe saltpeter is formed artificially by mixing animal refuse of all 
kinds with old mortar, wood-ashes, etc., in heaps, exposed to the air, but 
sheltered from the rain. These heaps are watered from time to time with t 
putrid urine, and after the lapse of two or three years the mixture is washed, 
and the salt crystallized out. A cubic foot of refuse may in this way be 
made to yield as much as 20 ounces of niter. ^ 

The earth on the floor of many caverns, as the Mammoth Cave of Kentucky, 
often becomes strongly impregnated with nitrate of lime, "wIiTcT^"wnen leached 
with wood ashes, or treated with potash, i s decomposed, and yields nitrate of 
potash. In this way saltpeter was manufactured for the Government during 
the war of 1812. 

504. P r opTr t i e s. — Saltpeter crystallizes in long, six-sided prisms, and 
is freely soluble in water ; its solubility increasing in a remarkable manner 
with the temperature of the water; thus, 100 .parts of water at 32° E. dissolve 
t parts; at 65° E.~, 29 parts; and at 212° F., 400 parts. The taste of salt- 
peter is cooling and saline; it is an antiseptic,* and is used in brine for pre- 
serving the natural color of salted meats. 

Owing to the great quantity of oxygen which saltpeter contains, and the 
facility with which it parts with it, it is extensively used as an oxydizing 
agent. When thrown upon burning coals it deflagrates brilliantly. If paper 
be dipped in a solution of niter, and dried, it forms what is well known as 
" touch-paper" which, when once kindled, steadily smoulders away till con- 
sumed, and is hence largely employed in firing trains of powder, fireworks, 
etc. 

The occurrence of fearful explosions, when warehouses containing saltpeter 
in large quantities have been consumed by fire, has occasioned much specu- 
lation as to whether ignited saltpeter will, under any circumstances, explode. 
The facts in regard to this subject are as follows ; — saltpeter, when burned by 
itself, will not explode ; but the oxygen, which is liberated during its ignition, 
by mingling with the carbonaceous gases evolved during the combustion, 
at the same time, of other substances, may produce explosive compounds. 



* The name antiseptic is given to those substances which resist and retard the decom- 
positioa of organic substances, such as saline bodies, acids, etc. 

Questions. — What is saleratus? From whence is saltpeter mainly obtained ? What 
is supposed to be its origin ? How may saltpeter be formed artificially ? What are the 
properties of saltpeter ? What is " touch-paper ?" Will saltpeter explode ? 



332 .^ORGANIC CHEMISTRY. 

505. Gunpowder . — The principal use of saltpeter is for the manufac- 
ture of gunpowder, which consists of a mechanical mixture of niter^ sulpliur, 
and charcoal, in proportions which very nearly correspond to_l^equ:vaient of 
niter, 3^ of carbon, and J. of sulphur; thus: — 

In 100 parts. 

Niter, 1 eq. 101 74/8 

Sulphur, XeqrTBT 13 -3 

Charcoal, 3 eq. 13 11-9 

135 100-0 

The great explosive power of gunpowder is due to the sudden conversion 
of the solid grains into gases (principally nitrogen and carbonic acid) ; these, 
at the ordinary temperature of the air, would occupy a space equal to about 
300 times the bulk of the powder used ; but from the intense heat developed 
at the moment of the explosion, the expansion amounts to at least 1,500 
times the volume of the powder.* 

506. Manufacture of Gunpowder. — In the manufacture of 
gunpowder, the three materials, in the state of the greatest purity, are first 
pulverized separately, and then mixed in the proper proportions. They are 
then slightly moistened, and further ground and blended together, in charges 
of 42 lbs. each, by means of large cylinders or wheels of iron, weighing sev- 
eral tons each, which roll round over the powder in a large wooden tub. The 
mixture is then spread in layers of about an inch in thickness, between cop- 
per plates, and subjected to an i'mmense hydraulic pressure. A thin, hard 
cake is thus obtained, which is broken into small fragments, or granulated, by 
subjecting it to the action of toothed, brass rollers, of different successive 
gauges. The grains are next sorted by means of sieves of different sizes ; 
after which they are thoroughly dried by steam-heat, and finally polished and 
glazed by rotating them in wooden revolving cylinders, with a small quan- 
tity of " black lead." 

The object of granulating the powder is to favor the rapidity of the ex- 
plosion, by leaving interstices through which the flame is enabled to pene- 
trate, and kindle every grain at the same moment. Powder, in the form of 
fine dust, burns rapidly, but does not explode. The firing of gunpowder is 
not absolutely instantaneous, inasmuch as gun-cotton and fulminating mer- 
cury explode much more rapidly — which facts prove duration in the explosion 



* The expansive force of gunpowder depends almost entirely upon the circumstances 
mider which it is fired. Count Rumford showed, during the last century, that if powder 
be placed in a closed cavity, and the cavity he two thirds filled, the force will exceed 
150,090 lbs. upon the Equare inch; and he estimated that if the cavity were entirely filled, 
and restrained to its original dimensions, the force would rise to 750,000 lbs. per square 
inch. Recent experiments, by Mr. Treadwell of Boston, also tend to confirm these con- 
clusions. On the other hand, if powder be fired ia constantly-maintained vacuum, it 
would not rend walls made of cartridge-paper, if a single end were left open to its escape. 

Questions. — What is gunpowder? To what is the explosive force of gunpowder due? 
How does its force vary? How is gunpowder manufactured ? Why is powder made in 
grains ? Is the explosion of gunpowder instantaneous ? 



sodium. 333 

of powder.* Substances which explode more rapidly than gunpowder are 
not adapted for the movement of projectiles, inasmuch as sufficient time is not 
given to allow the charge to receive the full advantage of the expansive force 
of the gases generated ; their action, therefore, is not to project the ball, but 
to burst the gun. 

The goodness of gunpowder may be tested by placing two small heaps upon 
clean writing-paper, three or four inches asunder, and firing one of them with 
a red-hot wire ; if the flame ascends quickly, with a good report, leaving tho 
paper free from white specks, and not burnt into holes ; and if no sparks fly 
off to ignite the contiguous heap, the powder is very good ; but if thesetests 
fail, tho ingredients are badly mixed or impure. 

SECTION II. 

SODIUM. 

Equivalent, 23. - Symbol, Ha (Natrium). Specific gravity, 0*972. 

507. History and Distribution. — This metal was first 
obtained by Davy, immediately after the discovery of 
potassium, by the voltaic decomposition of soda. It is 
now prepared very cheaply from the carbonate of soda, by 
a process analagous to that followed in the preparation of 
potassium. 

Sodium, in combination, occurs most abundantly in the mineral kingdom, 
though it is not so widely dilfused as potassium. Its great storehouse is 
common salt, from which substance most of the soda of commerce is obtained. 
" As potassium is in some degree characteristic of the vegetable kingdom, so 

* While the logical solution of this question adds hut little to our knowledge, -we are 
able to infer, from certain experimental results, the course of action which accompanies 
or causes the amazingly rapid explosion of a quantity of powder confined in a close cavity. 
44 Thus, when the fire reaches the charge from the touch-hole, the nearest grains become 
kindled, the hot fluid evolved is thrown further into the charge, and the burning succeeds 
successively until the pressure becomes so great as to condense the air contained between 
the grains sufficiently to produce the heat required for firing these grains, which are 
then consumed more or less rapidly as they are fine or coarse. We have then, first, 
the burning, in succession, of a small part of the charge ; then the immensely rapid, 
though not instantaneous, kindling of every grain composing it ; and then the consump- 
tion of these grains, which is not accomplished without time. It is a task for the concep- 
tion to grasp these events, following one another in distinct succession ; each having its 
beginning, middle, and end, and all being compressed in a period not exceeding l-200th 
of a second. When we have mastered the imagination of these we may go further, and 
combine with them the connected aud contemporaneous action of the ball, which passes 
from rest to motion, and through every gradation of velocity up to 1,000 feet per second, 
and leaves the gun as our historical period of l-200th of a second expires." — Tbeadwell. 

Questions. — Why are compounds more explosive than gunpowder not adapted for 
moving projectiles ? How is the goodness of powder tested ? What is said of sodium ? 
What of its occurrence in nature? 



334 INORGANIC CHEMISTRY. 

sodium is the alkaline metal of the animal kingdom, its salts being found in 
all animal fluids." 

508. Properties . — Sodium is a white metal, having the aspect of 
silver. It resembles potassium in its properties, but does not oxydate so 
readily as potassium, and when thrown upon water, does not inflame, unless 
the water has been previously heated. Sodium and all its salts, when ignited, 
communicate to flame a rich yellow color ; this reaction may be illustrated 
by holding a piece of soda glass, or any mineral containing soda, in the flame 
of a blow- pipe. 

509. The compounds of sodium have mainly the same composition and 
properties as those of potassium. 

510. Caustic Soda, or the Hydrate of Soda, NaO, HO, is prepared 
by decomposing carbonate of soda with quick-lime, in the same manner a.i 
has been already described for caustic potash. Its properties and appearanco 
are also exactly similar to those of caustic potash. 

511. Chloride of Sodium, IVaC 1. — Common ^dt ^This important 
and well-known compound is formed when sodium is ' ; ■**» <d in chlorine gas, 
and also when soda or its carbonate is neutralized by hydrochloric acid. 

The union of these two elements is attended with a most remarkable con- 
densation of volume. Thus 24 parts by measure of common salt contains no 
less than 25 -8 parts by measure of sodium (more than its own bulk), and no 
less than 30 parts by measure of liquid chlorine ; or in other words, 5 5 -8 
parts by bulk are compressed by the action of the force of chemical affinity 
into 24. "No known mechanical force," says Faraday, "could have accom- 
plished this result ;* and it is also strange that such an amount of condensa- 
tion — of squeezing together of atoms — should be co-existent with such perfect 
transparency, for common salt is even more transparent than glass, allowing 
a certain kind of radiant matter to pass which stands on the confines of light 
and heat." (§ 206.) 

512. Common salt is found pure or native in the earth in rock-masses 
(rock-salt), in various countries, and is regularly mined or quarried. The 
celebrated mine near Cracow, in Poland, is located in a bed of rock-salt 
which is estimated to be 500 miles in length, 20 broad, and not less than 
1200 feet thick. 

Salt also exists in solution in all sea- water, in a proportion of about 2-1 per 
cent., which amounts to nearly 4 oz. per gallon, or to a bushel in from 300 
to 350 gallons. Salt manufactured from sea-water by solar evaporation, is 
termed "bay," or "solar salt." The evaporation is not carried to dryness, 
but when the greater part of the chloride of sodium is deposited in crystals, 

* The student, in this connection, will do well to bear in mind, that physicists are not 
yet fully agreed as to whether a liquid is capable of any reduction of volume by any ap- 
plication of mecnanical pressure. 

Questions. — What are its properties? What is caustic soda? What is common salt? 
How may it be formed artificially ? What singular circumstance attends the union of its 
elements ? What is rock salt ? What proportion of salt exists in tea-water ? How i» 
salt manufactured from this source ? 



hwiim 



SODIUM. 



335 



Fig. 1T8.. 



the mother-liquor is drawn off. This, which from its bitter taste is tech- 
nically termed the " bittern," retains most of the other salts contained in 
sea- water, i. c, the compounds of magnesia, lime, bromine, etc. 

Salt is also manufactured in large quantities, especially in the United 
States, by evaporating the water of saline springs. From this source 6,000,000 
bushels were manufactured in the State of New York (principally in Onon- 
daga County) and 3,500,000 bushels in the State of Virginia, during the year 
135 G. The water of the Onondaga salt-springs contain about one seventh part 
of dry salt. The estimated amount of salt manufactured from all sources in the 
United States during the year 1856, was upward of twelve millions of bushels. 

The appearance of salt varies, according to the rate at which evaporation 
is conducted. When boiled down rapidly, it forms the fine-grained salt used 
upon our tables ; if evaporated more slowly, the hard, crystallized salt, pre- 
ferred for the packing of fish and meats, is obtained. 

Common salt crystallizes in cubes, which are anhydrous, but crackle or de- 
crepitate, when heated, from the water mechanically confined between their 
plates. If the evaporation of the solution J, of salt takes place slowly, the 
cubical crystals are large : but if it be rapid, they arc small, and curiously- 
arranged in what is called a " hopper-shaped" form. Thus, let us suppose a 
small cubical crystal has formed on the surface of the solution. From its 
greater density, the crystal has a ten- 
dency to fall to the bottom of the 
liquid, but capillary attraction keeps 
it upon the surface. (See Fig. 178.) 
New crystals soon form, which are 
joined to the first at the four upper 
edges, and constitute a frame above 
the first little cube. (See Fig. 179.) 
As the whole descends into the fluid, 
new crystals are grouped around the 
first frame, constituting a second. 
(Fig. 180.) Another set, added in 
the same way, gives the appearance 
shown in Fig. 181. The conse- 
quence of this successive arrange- 
ment is, that the crystals are group- 
ed into hollow, four-sided pyramids, 
the walls of which have the appear- 
ance of steps, because the rows of 
small cubic crystals retreat from each 
other. (See Fig. 182.) 

Common salt is equally soluble in hot and cold w ater ; 100 parts of water 
dissolve 37 parts of it; so that a saturated solution, or the strongest possible 

Questions. — From what sources is salt principally manufactured in the United States? 
What occasions the variations in the appearance of salt ? What is said of the crystalliz- 
ation of salt ? What of its solubility ? 




336 INOKGANIC CHEMISTRY. 

brine, contains 31 per cent. It is an essential constituent of the food of both 
man and animals^ who languish if it be supplied in insufficient quantities.* 

513. Sulphate of Soda, JV a , S O3 + 1 H .—This compound 
is popularly known as " Glauber salts," from its discoverer, Glauber. It has a 
saline, bitter taste, and is occasionally used in medicine as a purgative. It is 
found naturally as a mineral, and occurs also in sea- water, and in many min- 
eral springs ; it is generally prepared, however, by decomposing common salt 
with sulphuric acid, as in the process for preparing hydrochloric acid. 

Glauber salts possess the peculiar property of being more readily soluble 
in water atj^0° F. than in water at a higher, or at a boiling temperature. It 
crystallizes readily from a saturated solution in long four-sided prisms, which 
contain more than half their weight of water ; exposed to air, this water gra- 
dually evaporates, and the crystals crumble to a fine powder — ■effloresce. A 
very interesting experiment may be performed by closing hermetically a flask 
containing a boiling saturated solution of this salt ; in this condition, the so- ■ 
lution may be kept for months without crystallizing, but the moment air is 
admitted, the whole becomes a semi-solid mass of crystals. 

514. Carbonate of Soda,. NaO,C0 2 +10fiO. — Sal-Soda, 
Soda-Ash. — The preparation of this salt constitutes one 
of the most important branches of chemical manufacture ; 
immense quantities of it being consumed in the produc- 
tion of glass, in the fabrication of soap, in the operations 
of bleaching, and in the preparation of the salts of soda. 

The material from which carbonate of soda is now manufactured, is com- 
mon salt, and the details of the process are essentially as follows : a charge 
of 600 lbs. of salt is placed upon the hearth of a well-heated reverberatory 
furnace, f and an equal weight of strong sulphuric acid is poured upon it 



* " Salt," says Mungo Park, " is one of the greatest of all luxuries in Central Africa 
and the continued use of vegetable food creates so painful a longing for it, that no words 
can describe the sensation." From time immemorial, it has been known that without 
salt man would miserably perish, and among horrible punishments, entailing certain 
death, that of feeding culprits on saltless food is said to have prevailed in barbarous 
times. The explanation of this is, that the blood contains a very large percentage of 
common salt ; and as this is partly discharged every day through the skin and kidneys, 
the necessity of continued supplies of it to the healthy body becomes apparent. The bile 
also contains soda as a special and indispensable constituent, and so do all the cartilages 
of the body. Stint the supply of salt, therefore, and neither will the bile be able properly 
to assist the digestion, or the cartilages to promptly repair their waste.— Johnson. 

t A reverberatory furnace (Fig. 183), used extensively in the manufacture of soda-ash, 
the puddling and refining of iron, and in the smelting of metals, is a furnace so arranged 
that the heating is effected, not by the fuel itself, but by the flame passing from the fire- 
place, /, under the influence of a powerful draft, over a bridge into a chamber, where the 

Questions. — What of its necessity to man and animals ? What are Glauber salts ? 
What is said of them ? What of their solubility ? What of their crystallization ? What 
is soda-ash ? What is said of carbonate of soda ? From what is it manufactured ? De- 
scribe the process. What is a reverberatory furnace ? 



SODIUM. 



33T 



through an opening in the roof of the furnace. Hydrochloric acid is disen- 
gaged, which is usually allowed to escape up the chimney (§ 360), and the 
salt is converted into, sulphate of soda. This operation is completed in about 
four hours, and requires much care and skilL 

The sulphate thus formed is next reduced to powder, and mixed with an 
equal weight of chalk or limestone (carbonate of lime), and half as much fine 
coal. The mixture is then heated to fusion, with constant stirring, about 200 
lbs. being operated on at once. By this treatment double decomposition is 
effected, the sulphate of soda being converted . into carbonate of soda, and 
the carbonate of lime into sulphuret of calcium. The mass, when cold, is 
treated with water, the carbonate of soda dissolved out, and the solution 
subsequently evaporated to dryness. The product constitutes the soda-ash 
or British alkali of commerce (anhydrous carbonate of soda), and when of 
good quality contains from 48 to 52 per cent, of pure soda.* 




material to be acted upon is placed. The roof of this chamber 
being concave, reverberates or throws back the flame striking 
upon it to the floor beneath — hence the name, reverberatory fur- 
nace. The chamber has an opening upon the side, A, for the in- 
troduction of materials, and another opening at the end most dis- 
tant from the fire. The chimney is also provided with a damper. 
D, by which the draft is regulated. 

* The discovery and application of this method was one of 
those great events in the history of civilization which created or 
revolutionized whole branches of industrial art, and by cheapen- 
ing the production of 
great classes of art- 
icles of convenience 
and necessity, ma- 
terially improved the 
condition of the hu- 
man race. The pro- 
cess in question was 
devised by Leblanc, 
a French chemist, to- 
ward the close of the 
last century. It re- 
mained for a long 
time unnoticed, and it was not until 1820 that any successful trial was made with it in 
England. Previous to this, all the soda of commerce was obtained from the ashes of sea- 
weeds, which were sold in the market under the names of Spanish barilla and kelp; the 
former being produced on the coasts of France and Spain, and the latter chiefly on the 
coast of Scotland. Only a small quantity of the weight of these substances, however, was 
an alkali. The barilla contained about 18 per cent., and was sold for about $50 per ton; 
and the kelp only 5 or 6 per cent., and was worth $20 per ton. It is obvious, therefore, 
that the soap and glass-maker, in buying these substances, would, in the one case, pur- 
chase 95 parts of worthless material, and in the other 82 parts ; we say worthless, because 
of no service in the fabrication of soap or glass. It would seem, therefore, that the intro- 
duction of a strong and cheap alkali, would have been hailed by the manufacturers as one 
of the greatest advantages ; but the fact was quite the contrary, and the chemists and 
manufacturers found it extremely difficult to dissipate the prejudice in favor of kelp and 

Question. — What is said of the history and introduction of carbonate of soda ? 

15 



338 



INORGANIC CHEMISTRY, 



+ 






515. Bi-Carbonate of Soda, NaO, HO, 2C0 2) is obtained by 
passing carbonic acid gas into a solution of carbonate of soda, or by exposing 
soda-ash to the carbonic acid generated from fermenting grain, as in distiller- 
ies, etc. This salt is often sold under the name of "soda saleratus." 

516. Alkalimetry . — As the purity and value of the commercial car- 
bonates of potash and soda differ greatly, it becomes important to the buyer 

and the manufacturer to be able to determine rapidly and accu- 
" rately the quantity of available alkali in a given sample. Thi3 

operation, termed alkalimetry, consists in ascertaining how mucli^ 
dilute sulphuric acid of a standard strength is required to neutralize j 
exactly a known weight of a particular specimen. A good article J 
will require more acid than a poor one ; consequently, the amount 
of alkali present may be estimated from the quantity of acid con- 
sumed. In practical operations, an instrument called an alkali- 
meter is employed. This consists of a graduated glass cylinder, or 
Etube, divided into degrees (graduated) — Fig. 184) — in winch the 
acid used is measured instead of being weighed. For this purpose 
a test acid must be prepared, of such a strength that one degree 
of it will exactly neutralize one grain of pure alkali (potash, or 
soda). The number of degrees then consumed in neutralizing the 
alkaline properties of a known weight of a sample, in solution, will 
indicate at once, in per cents., the quantity of pure alkali in the ar- 
ticle tested. 
p J 517. Nitrate of Soda, Soda- Saltpeter, Cubic Niter, NaO, 

If. NO5, is a native product, occurring in great quantities in Peru and 

— "»" Chili, S. A. It resembles nitrate of potash in its properties, but 
can not be used in the manufacture of gunpowder, as it freely ab- 
sorbs moisture from the atmosphere. It is used, however, exten- 
tensively in the manufacture of nitric acid, and to some extent in agriculture, 
as a fertilizer. 



and barilla. "When, however, the soda-ash was once introduced, it so reduced the ex- 
pense of making soap, that the operation of alkalizing the fats, which had before cost $40 
per ton, was effected, in one third the time, for $10 per ton. Similar results followed its 
application to the manufacture of glass ; and the business of manufacturing soda-ash in- 
creased so fast, that in 1S3T, seventeen years after the establishment of the first manufac- 
tory in England, the quantity produced was 72,000 tons, and at the present time it ia 
upwards of 200,000. The saving to the English nation in the manufacture of soap alone, 
from the introduction of Leblanc's process, taking as a basis the former price of barilla, 
and the present consumption and price of soda-ash (1 ton of the latter being equivalent to 
S tons of kelp and 3 of barilla), was estimated in 1847 as equal to twenty millions of dol- 
lars per annum ; while the benefit to the world at large has been, that the prices of soap 
and glass have been reduced so low, that the poorest are not debarred from their unre- 
stricted use. 



QtfESTiONs.— What is said of bi-carbonate of soda ? What is alkalimetry? What of 
nitrate of soda ? 



^ 



VlA li 



THIUM. — AMMONIUM. 339 



SECTION III. 

LITHIUM. 

Equivalent, 6. Symbol, L. 

518. This rare metal forms the basis of the third alkali, 
Hthia, and resembles sodium in appearance and properties. 
The alkali, lithia (oxyd of lithium), occurs in small quan- 
tities in a few varieties of minerals, and is rarely met with. 

SECTION IV. 

AMMONIUM (HYPOTHETICAL). 

Equivalent, 18. Symbol, NH4. 

519. The alkali ammonia so closely resembles potassa 
and soda in its properties and in its salts, that chemists at 
the present time generally regard it as the oxyd of a com- 
pound metal, as the other alkalies are oxyds of simple 
metals. The name applied to this hypothetical metal is 
Ammonium, its composition beiug 1 atom of nitrogen, and 
4 atoms of hydrogen. 

All attempts to isolate this substance have failed, from its tendency to sep- 
arate into ammcnia and hydrogen gas. It can be apparently obtained, how- 
ever, in combination with mercury. This fact may be easily illustrated by 
the following experiment : — A little mercury is put into a test-tube, with a 
grain or two of potassium or sodium ;* on the application of moderate heat, 
over a spirit-lamp, combination ensues, with an evolution of heat and light. 
"When cold, the fluid amalgam is put into a little porcelain cup, and covered 
with a strong solution of sal-ammoniac (chloride of ammonium). A double 
decomposition immediately ensues : the chlorine and sodium unite to form com- 
mon salt, while the mercury at the same time commences to increase in bulk, 
and ultimately swells up until it acquires eight or ten times its original vo- 
lume, assuming a pasty consistence, without losing its metallic luster. Tha 
new substance, exposed to a temperature of 0° F., crystallizes in cubes, but 
if left to itself, is quickly decomposed, at ordinary temperatures, into fluid mer- 
cury, ammonia, and hydrogen. Now it is evident that the mercury has com- 
bined with something; but in no case where mercury or any other metal 



* The proportions should be about 100 of mercury to 1 of potassium or sodium, by 
■weight. 

Questions. — What is said of lithium ? What of ammonium ? How may the apparent 
production of this substance be illustrated ? 



340 INORGANIC CHEMISTRY. 

combines with a non-metallic substance, is there ever a retention of metallio 
properties after combination, as in this instance ; therefore, the inference is, 
that the substance which has entered into combination with the mercury is a 
metal — ammonium. 

The fact that a compound body — cyanogen — is generated from carbon and 
nitrogen, which comports itself in every respect like the non-metallic element 
chlorine, removes every difficulty in the way of our conceiving that a com- 
pound may also be formed from nitrogen and hydrogen, which may have the 
properties of a metal. 

According to the ammonium theory, all the salts of ammonia are derived 
from this radical, and correspond in constitution to the salts of the simple 
metals. 

520. Chloride of Ammonium, NH 4 CI.— Sal- Ammoniac— Thi3 
substance, which is a compound of ammonium and chlorine, is the most im- 
portant of all the salts of ammonium, and occurs naturally as a volcanic pro- 
duct. It was formerly imported from Egypt, as a product of distillation from 
dried camel's dung, and from its having been originally procured from a dis- 
trict in Northern Africa, near the temple of Jupiter Ammon, the name am- 
monia originated. It is now, however, manufactured in large quantities, from 
the ammoniacal liquors formed in the manufacture of coal-gas, and from the 
condensed products of the distillation of bones and other animal refuse, in the 
preparation of animal charcoal. These are first treated with hydrochloric acid, 
and the resulting liquors evaporated to dryness. The residue is then subjected 
to heat in iron vessels, when the chloride of ammonium volatilizes in dense 
white fumes, which condense, on cooling, into white, semi-transparent, fibrous 
masses, the sal-ammoniac of commerce. 

Sal-ammoniac has a sharp, acrid taste, corrodes metals powerfully, and i3 
readily soluble in water. It does not, however, possess the characteristic odor 
of ammonia. It constitutes the source from whence most of the salts of am- 
monia are prepared. 

521. Ammonia, N H 4 0. — Volatile Alkali, Hartshorn. — This alkali exists 
in the atmosphere, in the juices of certain plants, in clayey and peaty soils, 
and is freely evolved, in combination, from the craters of volcanoes. 

522. Preparation . — Ammonia can not, under ordinary circumstances, 
be formed by the direct union of its elements. A series of electric sparks, 
however, passed through a mixture of hydrogen and nitrogen, will, after a 
time, generate a limited quantity of it. The production of ammonia, on the 
contrary, by the indirect combination of hydrogen and nitrogen, is a circum- 
stance of continual occurrence. It especially takes place during the spon- 
taneous decomposition of animal and vegetable substances which contain 
hydrogen and nitrogen, and in almost every process of oxydation in the 

Questions. — Have we any reason to doubt the possibility of the existence of a com- 
pound metal ? What is sal-ammoniac ? What is said of its natural occurrence ? What 
■of its manufacture ? What is said of the natural occurrence of ammonia ? What of its 
production ? 



AMMONIUM. 



341 



Fig. 185. 



presence of moisture ; in the latter case, the hydrogen, at the moment of 
liberation (in a nascent state) from the water by deoxydation, enters into 
combination with the nitrogen of the atmosphere. 

• 523. Ammonia is usually obtained by subjecting a mixture of quick -lime 
and sal-ammoniac to a gentle heat in a flask or retort ; — the lime decom- 
poses the chloride of ammonium, forming chloride of calcium, and liberating 
free ammonia, which latter escapes as a colorless, transparent gas. The same 
mixture slowly evolves ammo- 
nia at ordinary temperatures, 
and is sometimes used for the 
filling of smelling-bottles. For 
experimental purposes, ammo- 
niacal gas is best prepared by 
heating a strong solution of 
ammonia in a glass retort, and 
collecting the evolved gas over 
mercury, or by displacement, 
as is represented in Fig. 185. 
When collected by displace- 
ment, the gas must be allowed 
to pass into the bottle until a 
piece of reddened litmus paper 
held to the mouth is imme- 
diately turned blue. The tube is then withdrawn, and the stopper, slightly 
greased, is inserted. 

524. Properties . — Ammonia thus produced is a gas, which is easily 
condensed to a liquid by a reduction of temperature ( — 40° F.) or by pres- 
sure. It has an extremely pungent smell, and instantly kills an animal im- 
mersed in it ; but when largely diluted with air, it is an agreeable stimulant. 
From the fact that ammonia was formerly prepared by distilling the horns 
of deers and harts, it is often popularly cafled "hartshorn." 

Ammonia does not support the flame of burning bodies, but is slightly 
combustible. A jet of gas directed across the stream of hot air issuing from 
a lighted Argand lamp,, burns with a pale green flame. It acts strongly as an 
alkali, turning vegetable-blues green, restoring the blue color of reddened 
litmus, and neutralizing the most powerful acids. The change, however, of 
vegetable colors produced by ammonia, owing to its great volatility, is not 
permanent ; but the vegetable substances regain their colors after a time by 
exposure to the air, which is not the case when the change is effected by the 
fixed* alkalies. Ammonia is, therefore, often called the " volatile alkali." 

Any volatile or gaseous acid brought into an atmosphere containing am- 
monia, produces a white cloud, from the formation of a solid salt. This 
property is often employed to detect the presence of ammonia in quantities 




Questions. — How is ammonia obtained practically ? What are the properties of am- 
monia ? Why is ammonia sometimes called hartshorn ? How may the presence of am- 
monia be detected ? 



342 



INORGANIC CHEMISTRY 




Fig. 187. 



too small to be recognized by their odor. The reaction may be illustrated by 
p , Rfi bringing a rod of glass, or a strip of wood moist- 

ened with dilute hydrochloric acid, near to a vessel 
or substance evolving ammonia ; — chloride of am- 
monium being formed. (See Fig. 186.) 

Water dissolves ammoniacal gas in large quan- 
tities, and with great rapidity ; — water at 50° F. 
absorbing about 6*70 times its volume. "When a 
piece of ice is introduced into a jar of gas standing 
over mercury, it instantly liquefies, and by condensing the gas forms a 
vacuum. The almost instantaneous absorption of this gas by water may be also 
illustrated by closely fitting a perforated cork and tube 
into the mouth of a jar containing ammonia, and in- 
verting the jar in a vessel of water. (See Fig. 187.) 
The first portiom of water that enter the jar absorb 
the gas so rapidly, that a vacuum is created, and a 
miniature fountain produced. 

525. Solution of Ammonia — The aqueous, 
solution of ammonia, known as aqua ammonia, liquid 
ammonia, etc., is a reagent much used in pharmacy 
and chemistry. It is a colorless, transparent liquid, and 
has all the pungent and alkaline properties of the gas. 
"When applied to the skin in a concentrated form, it blisters it, and is hence 
often termed caustic ammonia. Exposed to the air, ammonia escapes from 
it, and heat disengages it abundantly. 

526. There are several carbonates of ammonia. The ordinary sal-volatile 
of the shops, which constitutes the basis of the well-known " smelling-salts," 
is a sesqui carbonate of ammonia, 2NH 4 0, 3C02. It is a white solid, highly 
volatile, and when exposed to the air absorbs carbonic acid, and becomes 
converted into an inodorous bi-carbonate. This salt is frequently used by 
bakers in the place of yeast, for raising bread, cake, etc. — heat converting it 
into gas, which, escaping from the dough, renders it light and porous. 

527. flydrosulphuret of Ammonia, Sulphide of Am- 
monium, IV H 4 , S -f- H S . — This reagent, which is extensively employed 
in chemical analysis, is formed by transmitting sulphuretted hydrogen through 
a solution of ammonia to saturation. The solution thus prepared should be 
kept cold and in closed glass bottles. 

528. General Properties of the Alkali e s i^— The alkalies 
are the strongest bases known in chemistry. They are all soluble in water, 
have alkaline properties in the most marked degree, and exert a caustic and 
decomposing action upon organic substances. 

Most of the salts which the alkalies form with acids are soluble in water. 




Questions. — What is said of the absorption of ammonia by water ? How may this be 
Illustrated ? What is aqua ammonia ? What are its properties ? What is said of car- 
bonate of ammonia ? What is hydrosulphuret of ammonia ? What are the general prop- 
erties of the alkalies ? What is said of their salts ? 



BARIUM — STRONTIUM. 343 

This i3 especially true of their carbonates, which also exhibit alkaline prop- 
erties. Carbonic acid can not be expelled from the alkaline carbonates by 
heating, but it escapes immediately with effervescence, on the addition of 
other acids. 

"With the fats and fixed oils, the alkalies yield soaps, which are soluble in 
water. 



CHAPTER X. 

METALS OF THE ALKALINE EARTHS. 

529. The metals belonging to this class are Barium, 
Strontium, Calcium, and Magnesium. 

Their oxyds, baryta, strontia, lime, and magnesia, are called alkaline 
earths, because they possess an earthy appearance, together with some alka- 
line properties. The metals of the alkaline earths, like the metals of the al- 
kalies, are all characterized by an intense affinity for oxygen, and their isola- 
tion in a pure state is a matter of great difficulty. 

SECTION I. 

BAPwIFM AND STRONTIUM. 

530. Barium, — Equivalent, 68' 5 ; Symbol. Ba. — Barium 
is a white, malleable metal, which is fusible under a red 
heat. It was first discovered by Davy, and was named 
Barium (from (3apvg , heavy) in allusion to the great density 
of its compounds. 

The essential features of the method at present adopted for obtaining the 
metals of the alkaline earths, is to subject their chlorides to heat in contact with 
potassium, or sodium. These elements, from their greater affinity for chlorine, 
decompose the earthy chlorides, and leave their metallic bases in a state of 
greater or less purity. 

Baryta occurs in nature chiefly as a sulphate — sulphate of baryta, heavy 
spar — in beautiful, white, tabular crystals, often associated with copper or 
lead ores ; this mineral, when ground to powder, is extensively used for 
the adulteration of white lead. A native carbonate is, however, the source 
from whence most of the other preparations of baryta are obtained. 

The Chloride of Barium, BaCl, is the most common soluble salt of barium ; 

Questions. — What are the metals of the alkaline earths ? What are their properties T 
What their oxyds ? What is said of barium ? By what process are the metals of the 
alkaline earths obtained ? What is said of the natural occurrence of baryta ? What are 
its principal salts ? 






344 INOKGANIC CHEMISTRY. 

it is much used in chemical analysis as a test for the presence of sulphuric 
acid in solution — which unites with baryta to form a white, insoluble sul- 
phate. 

531. Strontium. — Fquivale?it, 44; symbol, Sr. — Stron- 
tium is a white metal, greatly resembling barium. 

Its oxyd, strontia, occurs in nature as a carbonate (the mineral, strontianite) 
and more abundantly as a sulphate (celestine). The most remarkable charac- 
teristic of the strontia salts, is that of communicating a magnificent crimson 
tint to the flame of burning substances. The red fires of the pyrotechnists 
are composed of nitrate of strontia, chlorate of potash, sulphur, and antimony. 
This reaction may be illustrated by inflaming a little alcohol, in which chlo- 
ride of strontium has been dissolved. 

SECTION II. 

CALCIUM. 

Equivalent, _2£L Symbol, Ca. 

532. Calcium is a light, yellow metal, of the color of 
gold alloyed with silver. It is very malleable, and can be 
hammered into leaves as thin as writing-paper. It melts 
at a red heat, and oxydkes in the air at ordinary temper- 
atures. In combination, as lime, it forms one of the most 
abundant and important constituents of the crust of the 
globe. 

533. Lime, C a . — Oxyd of Calcium. — Lime is obtained in a state of 
purity by heating pure carbonate of lime (calcareous spar) in an open crucible, 
for some hours, to full redness : the carbonic acid is driven off by the heat, 
and the lime remains. For commercial purposes, it is prepared by heating 
common limestone, which is an impure carbonate of lime, in a stone kiln or 
furnace, the interior of which is somewhat in the form of a hogshead, and is 
filled with alternate layers of limestone and fuel. The lime, as it is burned, 
gradually sinks down, and is removed by openings at the base of the furnace, 
while fresh supplies of fuel and limestone are supplied at the top. In this 
way the furnace may be kept in action for a great length of time without in- 
terruption. 

534. Properties . — Lime as thus prepared is termed " quicklime," or 
caustic lime, and in a state of purity has resisted all attempts to fuse it, 
"When water is poured upon quicklime, it swells up, and enters into combina- 
tion with the water, forming hydrate of lime, or slacked lime. If the propor- 
tion of water is about half the weight of the lime employed, a light, dry pow- 

Questionb What is said of strontium ? What is a characteristic of its salts? What 

is calcium ? How is lime prepared ? What is quicklime ? What is slacked lime ? 



CALCIUM. 345 

der is formed, accompanied with a powerful evolution of heat — sufficient to 
occasion the ignition of wood. The hydrate which is thus formed is a definite 
compound of J_equivalent of lime with L equivalent of water. Lime, also, 
when exposed to the air, slowly attracts both water and carbonic acid, and 
crumbles to white powder — "air-slacked lime." 

Lime is soluble in about 700 parts of water, forming what is called "lime- 
water." It is more soluble in cold than in hot water, the latter dissolving 
only half as much as the former. Lime-water is characterized by a nauseous 
taste, and decided alkaline properties. It restores the blue of reddened lit- 
mus, and changes the blue infusion of cabbage to green. Exposed to the air, 
it gradually absorbs carbonic acid ; a pellicle of carbonate of lime forms upon 
its surface, which, if broken, is succeeded by another pellicle, until the whole 
of the lime is separated from the solution, in the form of an insoluble car- 
bonate. 

Lime diffused through water forms milk or cream of lime. 

Quicklime exerts a corrosive and destructive action upon the skin, nails, 
and hair, and upon'" some vegetable substances. Advantage is taken of this 
property to remove the hair from hides, preparatory to tanning, by immersing 
them in milk of lime.* 1 

Lime is also largely employed as a manure, and is particularly valuable 
upon very rich vegetable soils, such as those formed from reclaimed peat-bogs ; 
its effects in these cases are due to the decomposition of the organic matter, 
which it renders soluWe and capable of assimilation, by plants. Lime formed 
from limestone, which contains much magnesia, is unsuited for agricultural 
purposes. Lime should not be mixed with manures in the state of decom- 
position, since it liberates the ammonia contained in them, and impairs their 
value as fertilizers. 

535. Mortars and Cements , — The most important practical appli- 
cation of lime is for the manufacture of mortars and cements. Pure lime, 
when made into a paste with water, forms a somewhat plastic mass, which 
sets into a solid as it dries, but gradually cracks and falls to pieces. It does 
not possess sufficient cohesion to be used alone as mortar. To remedy this 
defect, and to prevent the shrinkage of the mass, the addition of janjLis found 
to be necessary. 

The proportions of lime and sand in good mortar, vary ; the amount of 



* According to Dr. John Davy, of England, the opinion popularly entertained, that 
quicklime exercises a corr oding and destructive influence upon animal and vegetable mat- 
ter in general, and that animal bodies exposed to its action rapidly decompose and decay, 
is wholly erroneous. The results of numerous experiments made by him, seem to show, 
that with the exception oi the cuticle, nails, and hair, lime exerts no destructive action 
on auimal tissues, but that its influence is antiseptic. In the case of vegetable substances, 
also, the action was similar, and instead of promoting, it arrested fermentation. 

Qttestion.— When is lime said to be air-slacked ? What is said of the solubility of 
lime? What are the properties of lime-water? What is cream of lime? What is said 
of the caustic action of lime ? What of its uses in agriculture ? What is mortar ? What 
is the necessity of sand in mortar ? 

15* 



\ 



346 INORGANIC CHEMISTRY. 

sand, however, always exceeding that of lime, and generally in the proportion 
of 4- to 1. The more sand that can be incorporated with the lime the better, 
provided the necessary degree of plasticity is preserved. That sand is most 
suitable for mortar which is wholly siliciouSj, and whose particles are sharp, or 
not rounded by attrition. 

The cause of the hardening of mortar is not thoroughly understood ; the 
explanation generally given is, that the water gradually evaporates, and the 
lime, by a sort of crystallization, adheres to the particles of sand, and unites 
them together. A portion of the lime, also, by absorption of carbonic acid 
from the air, is gradually converted into carbonate of lime. In the course of 
time, also, a chemical combination takes place between the silica of the sand 
and the lime, forming a compound of silicate and hydrate of lime, which pos- 
sesses great hardness. This reaction explains the remarkable hardness often 
observed in the mortar of old buildings. 

It is an advantage to moisten bricks and stones before applying mortar to 
them, in order that they may not absorb water from the mortar, and thus 
cause it to set too rapidly. The completeness of the hardening of mortar, de- 
pends upon a thorough intermixture of the lime and the sand. 

536. Hydraulic Cements . — Ordinary mortar, when placed in water, 
gradually softens and disintegrates, while the lime dissolves away ; it can not, 
therefore, be used for subaqueous constructions. Some limestones, however, 
which contain about 20 per cent, of clay (silicate of alumina), afford lime 
which possesses the property of hardening under water. Such limes are 
known as hydraulic limes, or cements, and may be artificially imitated by mix- 
ing with ordinary lime a due proportion of clay not too strongly burnt.* 

Concrete is a mixture of hydraulic lime with small pebbles, coarsely 
broken. 

537. Carbonate of Lime, CaO,C0 9 . — This substance is one of 
the most abundantly diffused compoundTin nature. In its amorphous condi- 
tion it forms the different varieties of limestone, chalk, and calcareous marl ; 
it is also the principal constituent of corals and shells, and enters, to some ex- 
tent, into the composition of the bones of animals. 

The term limestone is applied to those stones which contain at least hal£ 
their weight of carbonate of lime ; and according to the other prevailing in- 
gredients, a limestone may be argillaceous (clayey), magnesian, ferruginous 
(containing iron), bituminous, foetid, etc. 

• * The rapidity with which different kinds of hydraulic limes set, varies with their com- 
position. If the clay do not exceed 10 per cent, of the mass, the mortar requires several 
weeks to harden. If the clay amount from 15 to 25 per cent., it sets in two or three days ; 
and if from 25 to 85 per cent, of clay he present, it sets in a few hours. The substance to 
which the term Roman cement is applied, is a lime of this latter composition. In order 
that hydraulic lime should properly harden, it should not be submerged until it begins to 
Bet.— Miller. 

Questions. — What is the cause of the hardening of mortar ? What advantage is it to 
moisten bricks, etc., before applying mortar ? What are hydraulic cements ? What is 
Roman cement? What is concrete? What is said of the distribution ef carbonate of 
lime ? What is a limestone ? 




CALCIUM. 347 

/ The term marble is applied to those varieties of compact limestone which 
I are capable of being worked in all directions, and also of taking a good polish. 
Carbonate of lime is found in a greater variety of Yig. 18?. 

crystalline forms than any other known substance. 
Its primary form is a rhombohedron, as seen in double 
refracting, or Iceland spar (see Fig. 187) ; but of this 
figure over 650 modifications are known to mineral- 
ogists. Carbonate of lime also crystallizes in another 
primary form, that of six-sided prisms, as in the min- 
eral aragonite. 

538. Carbonate of lime dissolves in pure water to the extent of about two 
grains to the gallon, but in water charged with c. arbfl nic. acid it is taken up 
freely, and again deposited as the gas escapes — often in anhydrous crystals. 
It is in this way that the enormous rock masses of crystalline carbonate of 
lime are supposed to have been formed. This action, which has been before 
alluded to, (§ 434), is beautifully illustrated in the formation of stalactites 
and stalagmites in caverns. "Water charged with carbonic acid and car- 
bonate of lime, falls in drops from the roof of the cavern ; but each drop 
before falling remains suspended for a time, during which a part of the car- 
bonic acid escapes, and a minute portion of carbonate of lime is left behind. 
It also deposits another minute portion of calcareous matter on the spot 
upon which it falls, and as the drops are formed nearly on the same spot for 
years together, a dependent mass like an icicle is formed from the roof — the 
stalactite ; while another incrustation gradually rises up from the floor beneath 
it — the stalagmite. In the process of time the two may meet and form a 
continuous column. (See Fig. 188.) 

539. Building Materials . — Carbonate of lime is a material much 
used in architecture and building, but all its varieties are not equally valuable 
for this purpose. Those varieties of marble which exhibit large crystals, or 
contain disseminated throughout their mass crystals of sulphuret of iron, have 
comparatively little strength, and are liable to disintegration. The stone of 
which the Washington Monument at Washington is constructed, is an ex- 
ample. On the other hand, very fine-grained porous limestones, and also 
those varieties of porous sandstones which are termed free-stones, are ill- 
adapted for the external portions of buildings, since they are liable to split 
into flakes after a few years' exposure to the weather. This generally arises 
from the absorption of water, and its expansion by freezing in the interior 
of the stone during winter. A simple and ingenious method of ascertaining 
whether a stone is liable to this defect, is to thoroughly soak a smoothly-cut 
block, one or two inches on a side, in a solution of sulphate of soda. On 
subsequently drying the block in the air, the sulphate of soda crystallizes in 

Questions. — What is marble ? What is said of crystallized carbonate of lime ? What 
is the supposed origin of crystallized carbonate of lime ? What are stalactites and stalag- 
mites ? Explain their formation ? What is said of the adaptability of carbonate of lime 
to building purposes? Why are porous stones liable to disintegrate? How may th« 
durability of a stone be tested ? 



348 INORGANIC CHEMISTRY. 

the pores of the material, and tends to split off fragments from its surface. 
The resistance which the stone opposes to this action affords a basis for ea 
timating its durability.* 

Fig. 188. 




540. Sulphate of Lime, C a , S 3 . — Gypsum. — This salt, as 
commonly met with, is a hydrate — CaO, S0 3 -f-2HO — and occurs abundantly 
in nature. In transparent plates it is termed " selenite," but in a fibrous, 
granular, compact, or earthy form it constitutes the different varieties of gyp- 
sum and alabaster. When ground to a fine powder, it is known in the 
arts as "Plaster of Paris," from the circumstance of the mineral being ex- 
tensively found in the vicinity of the French capital. 

Gypsum is extensively used in agriculture as a manuxs ; but its most re- 
markable property, and the one for which it is the most valued, is the power 



* In selecting a stone for architectural purposes, ire may be able to form a very good 
opinion of its durability and permanence, by visiting the locality from -whence it -was ob- 
tained, and observing the condition of the natural surfaces exposed to the weather. For 
example, if the rock be a granite, and it be very uneven and rough, it may be inferred that 
it is not very durable: that the feldspar, which forms one of its component parts, is mora 
readily decomposed by the action of moisture and frost than the quartz, another ingre- 
dient, and therefore that it is very unsuitable for building purposes. Moreover, if it pos- 
sess an iron-brown, or rusty appearance, it may be regarded as highly perishable, owing 
to the attraction which this metal has for oxygen — causing the rock to increase in bulk, 
and so disintegrate. 

The following is the comparative strength of some of our best-known building materials 
ia resisting a crushing force. The best varieties of Quincy granite (sienite) will sustain a 
pressure of 29,000 lbs. per square inch; good compact red sandstone, 9,000 lbs. ; a variety 
of sandstone called the " Malone," from northern New York, 24,000 lbs. ; ordinary mar- 
bles, from 7,000 to 10,000; the poorer varieties of sandstone, like that composing the 
body of the capitol at Washington, 5,000. 

Questions. — What is the constitution of gypsum ? Under what names is it known ? 
For Avhat is it used ? 



MAGNESIUM. 349 

it possesses, after it has been deprived of water by a heat not exceeding 
.300-° F., of again combining with water and forming a hard, compact mass. 
When the dried powder, known as " boiled plaster," is made into a thin paste 
.with water, the mixture becomes solid in a few minutes; a chemical combi- 
nation being formed of 2 equivalents of water and 1 of sulphate of lime, 
which eventually becomes as hard as the original gypsum. This power of 
resolidifying renders gypsum applicable for taking copies of objects of every 
description, and for the construction of molds and models. 

If the powdered gypsum is subjected to a heat much exceeding 300° F. it 
loses its property of solidifying when mixed with water. By mixing gypsum 
with 1 or 2 per cent, of alum, sulphate of potash, or borax, it forms, when 
mixed with water, a material much harder than ordinary plaster, and capable 
of taking a high polish. Artificial colored marbles, called "JScagliola" aro 
formed of gypsum, alum, isinglass, and coloring materials, incorporated into 
a paste. ^Stucc o is a combination of Plaster of JParis with a solution of gela- 
tine, or strong glue. 

541. Hyposulphite of Lime, CajO \ x S^Og is an abundant con- 
stituent of the refuse lime of gas-works, and by exposure to the air gradu- 
ally passes into sulphate of lime (gypsum). Gas-lime has been used for 
agricultural purposes, but it probably possesses little or no value as a fertil- 
izer. It has, however, been recommended for mossy land and for composts. 
All the hyposulphites act as depilatories, or hair-removers, and many of the 
depilatory powders sold by druggists are compounds of this character. 

542. Chloride of Calcium, CaCl, is formed by dissolving car- 
bonate of lime in hydrochloric acid. The saturated solution evaporated to 
dryness, and the residue fused, yields a white crystalline solid, which pos- 
sesses so great an attraction for moisture, that it is used for drying gases, and 
for depriving alcohol, ether, and other liquids, of water, by distilling them in 
contact with it. "When mixed with snow or ice, it forms a powerful freezing 
mixture. 

SECTION III. 

MAGNESIUM. 

Equivalent, 12. — Symbol, Mg. 

543. Magnesium is a malleable metal of the color of silver, and in combin- 
ation, is an abundant constituent of the crust of the earth. Associated with 
lime, as a double carbonate of lime and magnesia (oxyd of magnesium), it 
forms magnesian limestone, or dolomite. United with silica, as a silicate of 
magnesia, it enters more or less extensively into the formation of many rocks, 
and a great variety of minerals — such as soapstone or steatite, serpentine, talc, 

Questions.— What are its properties ? How may plaster of Paris be hardened ? What 
is scagliola? What is stucco ? What is said of hyposulphite of lime ? What of the ag- 
ricultural value of gas-lime? What peculiar property do all the hyposulphites possess? 
What is said of chloride of calcium? What is said of magnesium and its distribution? 
What is dolomite ?. Of what minerals is magnesia a principal constituent ? 



350 INORGANIC CHEMISTRY. 

meerschaum, etc. — all of which are nearly pure silicates of magnesia. Tho 
presence of oxyd of magnesium in rocks or minerals in considerable quantity, 
may be recognized by a peculiar slippery or greasy feeling which it imparts 
to them — hence the name " soapstone." Magnesium, also, exists abundantly 
in all sea-water, in combiuation with chlorine, iodine, and bromine. 

544. Oxyd of Magnesium, MjjQ . — Calcined Magnesia. — This 
substance, forming a white, very light, bulky powder, is left when carbonata 
of magnesia is heated to redness. It is much used in medicine as a mild and 
gentle aperient. 

545. Sulphate of Magnesia, M j , S 3x constitutes the well- 
known purgative medicine, Epsom Salts. It is manufactured largely from 
the bittern, or mother-liquor left after the partial evaporation of sea-water, 
by the addition of sulphuric acid to the solution of chlorides, and also by treat- 
ing serpentine rock with sulphuric acid. It possesses a bitter, disgusting 
taste, and readily crystallizes from solution in small prismatic crystals. 

546. Carbonate of Magnesia, M_g , C 2 — -The common, white 
magnesia of the shops is formed by precipitating a solution of sulphate of mag- 
nesia by a solution of carbonate of soda. It is insoluble in water, but a solu- 
tion of carbonic acid dissolves it, and forms the popular medicine known as 
Murray's "fluid magesia." Carbonate of magnesia also occurs as a mineral. 

547. Properties of the Alkaline Earths, — The alkaline 
earths are, next to the alkalies, the strongest chemical bases. They have a 
caustic action, but far less so than the alkalies, and form with fats, soaps 
which are insoluble in water. The carbonates of the alkaline earths are in- 
soluble in water, and when exposed to a powerful heat, part with their car- 
bonic acid — in this respect, being the opposite to the carbonates of the 
alkalies. 



CHAPTER XI. 

METALS OF THE EARTHS. 

548. The metals of the earths are. Aluminum, Glucin- 
ium, Zirconium, Thorium, Yttrium, Erbium, Terbium, 
Cerium, Lantanium, and Didymium. 

Of these, all but the first, aluminum, are extremely rare, and comparatively 
unimportant. Glucinium is the metallic base of the earth glucina, which is 
the characteristic constituent of the emerald and the ber}d. Zirconium is the 
metallic base of the earth zirconia, which is found in the gems, zircon and 
hyacinth. The others possess few points of general interest. 

Questions. — What is a characteristic of niagnesian minerals? What is calcined magne- 
sia? What are Epsom salts? How are they obtained ? What is said of carbonate of 
magnesia ? What are the characteristic properties of the alkaline earths ? What arc tha 
metals of the earth ? What is said of their occurrence in nature ? 



ALUMINUM. 351 



SECTION I. 

ALUMINUM. 

Equivalent, 13 '7. Symbol, AL Specific gravity, 2-5. 

549. The metal aluminum was first obtained by "Wohler, an eminent Ger- 
man chemist, in 1827. Comparatively little, however, was known of it until 
within the last few years, but processes have been recently devised by its dis- 
coverer and M. Deville of Paris, by which it is obtained, in considerable quan- 
tities, at a cost which (at present) renders it about twice as valuable as silver. 

Pare aluminum is a beautiful, white metal, closely resembling silver in color 
and hardness. Its most striking characteristics are, that, while it closely re- 
sembles in appearance the dense, heavy metals, it is in fact lighter than glass ; 
and, also, its power of resisting oxydation — not tarnishing by exposure to air 
or moisture, or even when heated to a red-heat. It fuses at a temperature 
below the melting point of silver, is malleable, ductile, and remarkably son- 
orous. Nitric and sulphuric acids, even when concentrated, scarcely attack it 
at ordinary temperatures; but it dissolves freely in hydrochloric acid, and 
even in strong vinegar (acetic acid). Aluminum derives its name from alum, 
into the composition of which it enters. 

The properties of aluminum are such as to give it a high industrial value ; 
and it has been applied to some extent for economic purposes. 

550. Oxyd of Aluminum, Alumina, A1 2 3 . — This is the only 
known oxyd of aluminum (a sesquioxyd). It occurs in a state of purity, 
with the exception of a little coloring matter, in the sapphire and the ruby ; 
the first of which is blue, and the latter red. These gems are only inferior in 
hardness, luster, and value, to the diamond. Emery, (corundum), which, from 
its hardness, is so largely used in grinding and polishing, is also nearly pure 
alumina. Next to silica, alumina, in combination, is the most abundant min- 
eral constituent of the crust of the earth. 

By mixing a solution of alum with an excess of ammonia, we obtain a 
white, semi-transparent, bulky precipitate — hydrate of alumina, Al20*3-f-3HO. 
This, washed, dried, and strongly ignited, furnishes a pure alumina, in. the 
form of a white powder, almost insoluble in acids, and infusible, except be- 
fore the oxy hydrogen blow-pipe. 

551. Alum . — Common alum is a combination of the sulphate of alumina 
and the sulphate of potash, with 24 equivalents of water. The constitution 
of this double salt may be represented as follows : A1 2 3 , 3S0 3 -f-KO,S03-f- 
24HO. "When alum is heated, it froths up, loses its water of crystallization, 
and is converted into a white, porous mass, many times the volume of the 
salt employed ; in this condition it is known as anhydrous, or burnt alum. 

Alum is occasionally found as a natural product in the earth, but for indus- 

Qttestioxs.— What is said of aluminum ? What are its properties ? What is the form- 
ula of alumina ? In what substances is it found pure ? What is said of hydrous and 
anhydrous alumina ? What is alum ? Give its formula ? What is burnt alum ? 



■■■•55 



352 



INORGANIC CHEMISTRY 



trial purposes it is manufactured artificially. The sulphate of alumina, which 
enters into its composition, may be obtained by dissolving alumina from com- 
mon clay by sulphuric acid, or by exposing certain aluminous (clayey) slates 
and shales, which contain sulphuret of iron (iron pyrites), to the action of the 
air, or to a moderate heat ; under these circumstances, the sulphuret of iron 
is decomposed, its sulphur uniting with oxygen to form sulphuric acid, which, 
subsequently, combines with the alumina of the clay to form sulphate of al- 
umina. This salt, obtained in solution from the clay by washing, is mixed in 
large casks with sulphate of potash, in proper proportions, and the whole al- 
lowed to stand. The formation of alum immediately commences, and after 
the lapse of a few weeks, the interior of the cask becomes lined with a thick 
mass of crystals. The staves of the cask are then removed, and an enormous 
mass of alum crystals, of the shape of the cask, is left standing. (See Fig. 
189.) These, when drained and broken up, furnish alum ready for marker. 

Fig. 189. 




Ordinary alum has a sweetish, astringent taste, and crystallizes very read- 
ily in regular octohedrons. 

552. The constitution and formation of alum affords a good illustration of 
the principle of isomorphism. For example, we may substitute in its manu- 
facture in the place of sulphate of potash, sulphate of soda, or sulphate of am- 
monia, and thus obtain soda, or ammonia alums, which crystallize in the 
same form as the potash alum, and possess similar properties ; or we may 

Questions. — How is alum manufactured ? What are its properties ? How does the 
constitution and formation of alum illustrate isomorphism ? 



ALUMINUM. 353 

substitute iu the place of the sesqui-oxyd of alumina AL2O3, sesquioxyds of 
iron, chromium, or manganese, without changing the original octohedral, 
crystalline form. These substitutions will be more clearly understood from an 
examination of the annexed table : 

Potash alum AI2O3, 3S03+KO, SO-3+24IIO 

Soda alum AI2O3, 3S03+NaO, SOa+241-IO 

Ammonia alum AI2O3, S8O3+NH4 O, SO-3+24HO 

Iron alum Fe203, 3SC-3+KO, S03+24HO 

Chrome alum O2O3, 3SC-3+KO, SQ3-f 24HO 

All these compounds are called alums, and are said to be isomorphous, be- 
cause they possess a similar chemical constitution, and the same crystalline 
form. They may be easily prepared by dissolving together in water their 
simple constituent salts in proper proportions, and allowing the solution to 
crystallize. Potash, soda, and ammonia alums are white, chrome alum a deep 
purple, and iron alum a pale purple, or red. 

Alum, and the compounds of alumina formed from it, are largely used in 
dyeing, calico printing, and in tanning. Alumina has a very great attraction 
for certain kinds of organic matter, and especially for coloring substances. 
To such an extent is this the case, that the hydrate of alumina is extensively 
employed in the place of animal charcoal for decolorizing animal and vege- 
table solutions. If cloth is soaked in a solution of alumina, prepared from 
alum, a portion of the earth attaches itself to the fibers ; and if subsequently 
plunged into a bath of coloring matter, it becomes permanently dyed. Most 
coloring substances, without this treatment, would be removed by washing ; 
but the presence of alumina seems to serve as a bond of union between the 
color and the fiber, which renders the adhesion of the dye permanent ; a few 
other substances, such as binoxyd of tin, and the sesquioxyds of chromium 
and iron, act in the same manner, and are called mordants (from the Latin 
mordeo, to bite in). 

"When alum is added to a colored vegetable or animal solution, and the 
alumina precipitated by the addition of an alkali, it carries down with it the 
greater portion of the coloring substance, and forms a class of pigments 
called lakes. Carmine is a lake prepared in this way from a solution of co- 
chineal. 

553. Silicates of Alumina . — The salts of silicic acid and alumina 
comprise a great number of important and interesting mineral substances. 

554. Clay . — All the varieties of clay consist of hydrated silicate of alu- 
mina, more or less mixed with other matters derived from the rocks, which 
by their decomposition have formed clay ; such as potash, uncombined silica, 
oxyd of iron, lime, and magnesia. According as one or the other of these 
ingredients predominates, the character of the clay and its adaptation to 
specific purposes will vary. 

Questions. — What are the uses of alum ? What property characterizes hydrous alu- 
mina ? How does alumina act in dyeing ? What are lakes ? What is carmine ? What 
is clay ? 



354 INORGANIC CHEMISTRY. 

Clays which are nearly free from oxyd of iron or carbonate of lime, are 
termed fire-clays, and are used for the manufacture of fire-bricks and cruci- 
bles ; such clays are of rare occurrence. Pipe-clay, used for the manufacture 
of tobacco-pipes, is a fine white clay, nearly free from iron. "When the pro- 
portion of carbonate of lime in a clay is considerable, it constitutes what is 
known as a marl ; if the aluminous constituent predominates, it forms an 
aluminous marl; if the carbonate of lime be in excess, it is a calcareous 
marl ; the latter is highly valued in agriculture as a fertilizer for light, sandy 
soils. Loam is a mixed substance containing much clay, some sand, iron, and 
a varying proportion of organic matter. Ochres are clays colored red or yel- 
low by oxyd of iron ; they are extensively used as paints. Fuller's earth is a 
porous silicate of alumina, which has a strong adhesion to oily matters ; if 
made into a paste with water, and allowed to dry upon a spot of grease on 
a board or cloth, it removes most of the oil by capillary attraction. It owes 
its name to the fact that it is employed to remove the grease applied to wool 
in spinning. 

555. Clay emits a peculiar odor when breathed upon, which is known as 
an argillaceous odor. When mixed with a soil, it gives it firmness and con- 
sistency, and retains the moisture, ammonia, carbonic acid, and organic mat- 
ters which contribute to the support of plants. In this way it indirectly 
ministers to the wants of vegetation, although alumina itself is not known to 
enter as a constituent into the structure of either plants or animals. 

Among other important minerals of which silicate of alumina is a prin- 
cipal constituent, may be mentioned feldspar, mica, all the varieties of slates, 
and lavas, trap, basalt, porphyry, etc. The gems, topaz and garnet, are also 
in great part silicate of alumina. 

The beautiful artificial blue pigment known as ultramarine consists mainly 
of silicate of alumina fused with sulphide of sodium. 

556. General Properties of the Earths . — The earths are 
entirely insoluble in water, and do not combine with carbonic acid. They 
possess weak basic properties, and alumina in some instances may even act 
the part of an acid. The metals of the alkalies, the alkaline earths, and the 
earths, are all of a low specific gravity, and are sometimes called, on this ac- 
count, the light metals, to distinguish them from the other metals, which are 
dense and heavy. 

Questions. — "What is fire-clay? What is pipe-clay ? What are marls ? What is loam? 
What are ochres ? What is "fuller's earth?" What are the properties of clay? What 
m ipftT.a.ifl w roa^y composed of silicate of alumina ? What is ultramarine ? What aro 
the general properties of the earths ? 



GLASS AND POTTERY. 355 

CHAPTER XII. 

GLASS AND POTTERY. 

557. Glass is a compound substance produced by fusing 
together, by a high and long-continued heat, mixtures of 
the silicates of jgotash, soda, lime, magnesia, alumina and 
lead — the nature and proportions of the ingredients vary- 
ing according to the purpose for which the glass is to be 
used. 

Silica fused with the alkalies, potash, or soda 2 readily yields a transparent 
glass of easy fusibility, buTnot adapted for economic purposes, since it is un- 
able to resist the action of water and acids. If the proportions are 3_of al- 
kali to 1^ of silica, the compound is so readily soluble in water as to be 
designated as "soluble glass." (§ 414.) By increasing the pioportion of 
silica, we can greatly diminish the solubility of the alkaline silicates, but 
not entirely so On the other hand, ^ilica fused with lime, magnesia, 
baryta, or alumina, yields compounds which resemble porcelain rather than 
glass, are entirely insoluble, and melt at only a high temperature. No single 
silicate is, therefore, adapted by itself to form glass, but by judicious mix- 
ture of the various silicates we can contain compounds which are transparent, 
free from color, fusible at a moderate heat, and insoluble in water.* 

The temperature at which glass fuses depends upon the amount of silica it 
contains ; the greater the proportion, the less the fusibility. 

558. The principal varieties of glass are as follows: — 

Common, colorless, or white glass, which is used for making tumblers, win- 
dow-glass, and looking-glasses, is a compound of silicate of potassa or soda, 
with silicate of lime. The character of the glass, however, varies very much 
according as one or the other of the alkalies is used. Glass composed of sim- 
ply the silicates of potash and lime,, is exceedingly transparent, very hard, and 
of difficult fusibility. It is highly prized in the laboratory for its adaptation to 
certain chemical requirements. The celebrated Bohemian glass — the finest 

* In strictness, the best-made*glass is to a certain extent soluble. If very finely-pow- 
dered window-glass be placed on turmeric paper, and moistened, it will exhibit an alkaline 
reaction. Windows in old houses often show prismatic colors, owing to the circumstance, 
that the long-continued action of rain and moisture has washed out the alkali of the glass, 
and left an irregular condition of surface, which occasions a refraction of light. Specimens 
of ancient glass which have been dug out of the tarth, often exhibit a pearly luster, re- 
sulting from pure silica, the alkali having been slowly removed by long exposure to 
damp. 

Questions.— What is glass ? Why is a mixture of silicates necessary for the formation 
of durable glass? What is said of the fusibility of glass? What is the composition of 
common white glass ? What is the character of potash-glass ? What is Bohemian glass ? 



356 INOKGANIC CHEMISTRY. 

glass produced, is a silicate of potash and lime, with a little silicate of alum- 
ina. By substituting^soda in the place of potash, we obtain a more fusibie, 
but a less transparent glass ; varieties of glass with this composition, are 
known as " crown glass," plate-glass, window-glass, etc. The presence of 
soda in glass imparts to it a blueish-green tinge, which is not observed when 
potash alone is used. 

Green Bottle Glass, and other inferior desciptions of glass used 
for the manufacture of articles in which color is not regarded, consist of an 
alkali, silica^ lime, ma^jjluniina-,; the cheapest and most ordinary materials 
~Ueihg used, such as wood-ashes and common salt, as alkaline products, com- 
mon sand, clay, gas-lime, and the refuse lime and alkali left after the manu- 
facture of soap. The green color of bottle-glass is due mainly to the presence 
of oxyds of iron and manganese. 

Flint-Glass, so called from the circumstance, that the silica used i» 
its manufacture was formerly derived from pulverized flints, is a mixture of 
silicate of potash and silicate of the oxT_d_ofleadi., It fuses at a lower temper- 
ature than the ordinary varieties of glass, has a beautiful transparency, and a 
comparative softness, which enables it to be cut and polished with ease. 
Glass which contains lead possesses the property of refracting light in a re- 
markable manner, ahais consequently employed for~the construction of 
buses for optical instruments, glass prisms, chandelier-drops, etc.; it is, also, 
the basis of the artificial gems known as paste, which are colored by metallic 
oxyds. 

559. The ^silic^jased for the manufacture of fine^glass is generally in the 
form of pure white sand, entirely free from oxyd of iron. Such sand is by no 
means common, the finest in the world being at present found among the 
Green Mountains of "Western Massachusetts, from which localities large quan- 
tities are annually exported to Europe. The silica- of the Bohemian glass is 
obtained by pulverizing masses of pure white quartz. The alkali used is a 
refined carbonate of potash or soda. These two ingredients, with a proper 
proportion of air-slacked lime, or oxyd of lead, are thoroughly mixed, and 
fused in large crucibles of refractory fire-clay, in a circular reverberatory fur- 
nace. This furnace is usually in the form of a truncated cone, 60 to 80 feet 
high, and 40 to 50 feet in diameter at the base. The furnace is at the center 
of the cone, and the glass-pots, to the number of 4 to 10, are arranged around 
the circumference, and opposite to openings in the walls of the furnace. Fig. 
190 represents the exterior of the furnace, and the general appearance of a 
glass-house. 

The fire of a glass furnace is never allowed to slacken, and the melting-pots 
remain permanently in their situations for several months, being charged from 
the exterior. A heat of about forty-eight hours is requisite to convert the 
crude materials into a liquid, homogeneous glass. 

Questions. — What is the character of soda-glass ? What is the composition of green 
bottle-glass ? What is flint-glass ? In what form is the silica used in the manufacture of 
glass? What its alkali? How is glass formed? 



GLASS AND POTTERY 



357 



The details of the working and molding of glass are purely mechanical, and 
a description of them is foreign to the object of this work. 

560. Colored Glass . — Glass is colored by the addition to it, in a fu_S£d- 
state, of small quantities of the metallic oxyds^ which dissolve in it without 




affecting its transparency. Thus, oxyd of cobalt imparts a deep blue ; oxyd 
of manganese, a purple or violet; oxyd of copper, a green; oxyds of iron, a 
dull green or brown ;' and oxyd of gold, a ruby or rose color* 



* Cut-glass ornamental articles, which exhibit different colors upon the same specimen, 
and at different depths in the thickness of the glass, are manufactured in the following 
manner : the object is first formed in white, transparent, and colorless glass ; then, being 
allowed to cool until it acquires solidity and consistency, it is dipped for a moment in a 
pot of colored glass in a state of fusion, and being suddenly withdrawn, it carries away 
upon it a thin coating of colored glass, which immediately hardens upon it, and becomes 
incorporated with it The article is then shaped by the processes of the glass-maker, and 
if it be afterwards cut, those parts which are cut will disclose the clear, transparent glass, 
While the parts not cut remain coated with the color. It is by this process that all the effects 

Question. — How is glass colored ? 




358 INORGANIC CHEMISTRY. 

561. Enamel is a term given to glass which is rendered milk-whito 
opaque by the addition of binoxyd of tin. Examples of such enamels are to 
be seen in watch-dials, and in the s>called porcelain transparencies. Colored 
enamels are produced by the addition of metallic oxyds to white enamels. 

562. Annealing . — If glass be allowed to cool suddenly after fusion, it 
becomes exceedingly brittle, and articles made from it are liable to break in 
pieces from the least scratch or jar, or even from a slight but sudden chango 
of temperature, as when transferred from a cold to a warm room. 

This property is strikingly illustrated by what are called Prince Rupert's 
drops, which are little pear-shaped masses of glass, formed by 
Fig. 191. dropping melted glass into cold water. (See Fig. 191.) These 
may be subjected, without breaking, to considerable pressure, 
or even to a smart stroke, but if the little end of the drop be 
nipped off, the whole mass instantly flies in pieces with a sort 
of explosion, and is converted into powder. This effect ap- 
pears to be due to the fact, that the particles of which these 
little masses are composed, are in a state of unequal tension, owing to the 
formation of a solid coating upon the exterior, while the interior parts are still 
fluid ; the latter being thereby prevented from expanding, as they become 
solid. The drops will bear a concussion because the mass then vibrates as a 
whole, but if the end bo broken, a vibratory movement is communicated 
along the surface without reaching the internal parts ; this allows them some 
expansion, which overcomes the cohesion of the outer coating, and the wholo 
at once flies in pieces. To obviate, therefore, this tendency to brittleness, all 
glass articles, after their manufacture, are subjected to the operation of an- 
nealing, which is a very slow and gradual process of cooling, by which the 
parts are enabled to assume their natural position with regard to each other. 
In some cases, several days, or even weeks, are required for the cooling of 
particular articles. 

563. Pottery and Porcelain. — The basis of all earthen- 
ware, porcelain, and china, is silicate of alumiaa (clay) . 

Pure silicate of alumina, however, contracts greatly and unequally on dry- 
ing, and, consequently, is unfitted to be used by itself for fictile purposes. 
This difficulty is, however, overcome by the addition to the clay of a propor- 
tion of silica, and to compensate for a loss of tenacity in the clay thereby oc- 
casioned, it is also customary to incorporate witn the mass some fusible 
material, as an alkali, silicate of lime, etc., which, at the temperature required 
for baking the ware, fuses, becomes absorbed by the more infusible portion, 



■which are seen in ornamental articles, which consist partially of colored, and partially of 
clear glass, are produced. Additional colors may also be combined on the article in the 
sama manner, and by cutting a surface so coated, to different depths, varieties of effects 
may be produced, involving a display of two or more colors. 

Questions.— What are enamels ? What effect is produced by allowing glass to cool 
suddenly? How is this illustrated by Prince Rupert's drops? What is annealing? 
What is the basis of all earthenware ? Why can not pure clay be used alone ? 



GLASS AND POTTERY. 359 

and binds the whole, on cooling, into a solid mass. According to the greater 
or less proportion of these fusible materials, the ware is more or less transpa- 
rent, or resembles glass in a greater or less degree. 

564. Porcelain is the name applied J;o the finest varieties of earthen- 
ware. It is composed of a very pure, white clay, called " kaolin" (derived 
from the decomposition of feldspar), very finely-divided silica, prepared by 
crushing and grinding calcined_-flinte ii _and a little lime. The utmost pains 
are taken to thoroughly incorporate these ingredients, and to avoid the intro- 
duction of particles of grit, or other foreign bodies. The mixture, having the 
consistency and appearance of dough, is then fashioned upon a peculiar kind 
of lathe — called a "potter's wheel," — or in molds'of plaster of Paris, into ware, 
— dried, and baked in a kiln or oven for a period of about 40,, hours. The por- 
celain in this condition is technically termed biscuit, and is~cbmpact and solid, 
but so porous as to readily imbibe water, and even allow it to filter through 
its substance. This difficulty is remedied by covering the ware with a glassy 
coating called a glaze, which generally consists of a more fusible mixture of 
the same materials as the porcelain itself. These, in a state of fine powder, 
are made into a cream with water, and into this the ware is dipped for a mo- 
ment, and then withdrawn ; the water sinks into its substance, leaving the 
powder evenly spread upon the surface, which, when submitted to a moder- 
ate heat, fuses, and forms a uniform, vitreous coating. In ornamented porce- 
lain, the designs are printed or painted upon the surface with various metallic 
oxyds, which develope their colors only after fusion with the ingredients of 
the glaze. 

The material called "Parian," of which statuettes, etc., are manufactured, 
is a carefully-prepared variety of porcelain. 

The details of the manufacture of the ordinary varieties of " stone" and 
" earthen" ware, are in principle the same as those involved in the manufac- 
ture of porcelain, less care, however, being taken in the selection of materials, 
and less labor being bestowed upon their preparation. The coarser kinds of 
earthenware are sometimes covered with a yellowish-white glaze, of which 
jjxydof lead is an important ingredient. The use* of such vessels in culinary 
operations is highly Objectionable, inasmuch as the lead is liable to be dis- 
solved off by acids, and act as a poison. 

Bricks and common pottery-Ware owe their red color to the iron naturally 
contained in the clay of which they are composed, which, by heating, is con- 
verted into red oxyd of iron. Some varieties of clay, like that found near 
Milwaukee, contains little or no iron; and, consequently, the bricks made from 
it are all light-colored. 

Questions. — What is the composition of porcelain? Describe its manufacture. How 
is porcelain ornamented with colored figures? What is "Parian?" How does the 
manufacture of earthenware differ from porcelain? How is earthenware sometimes 
glazed ? Why is the use of vessels glazed with lead dangerous ? Why are bricks and 
flower-pota red ? 



360 INOJtGANIC CHEMISTRY. 

CHAPTER XIII. 

THE COMMON, OR HEAVY METALS. 

SECTION I. 

iron (Ferrum). 

Equivalent, 28. Symbol, Fe. Specific gravity, 7*8. 

565. Natural Ilislory and Distribution.— Iron is the 
most abundant, the .most widely diffused, and the most 
useful of all the metals. It is the only metal which enters 
into the structure of all the vertebrate animals, as an es- 
sential constituent (existing always in the blood), and the 
only one whose oxyds are not injurious to either animals 
or plants. 

Iron in a metallic and malleable state, alloyed with nickel, cobalt, and small 
quantities of other metals, is found upon the surface of the earth in large 
^masses of meteoric origin. These masses are so peculiar in their composition 
and structure, and differ so essentially from all terrestrial substances, that 
although they may not have been seen to fall, they are easily recognized. 
Some of these extraordinary bodies are from 15 to 20 tons weight; one ob- 
served to fall from the atmosphere in an ignited state in South America in 
1844, was upward of a cubic yard in dimensions. A specimen in the cabinet 
of Yale College weighs 1,635 lbs., and one in the Smithsonian Institution, 
252 lbs. The occurrence in nature of metallic iron of a terrestrial origin is 
exceedingly rare. It is, however, said to be occasionally found associated 
with ores of platinum, and also in little nodules inclosed in masses of iron ore 
— the latter being evidently the result of electro-galvanic agency. Recent in- 
vestigations by Hayes of Boston have also rendered it probable that a deposit 
of native iron exists on th£ "West Coast of Africa, in the vicinity of Liberia. 

Iron in a state of perfect purity is not found also as an article of com- 
merce^ — the very best artificial irons always containing some carbon, and 
generally minute quantities of silica, sulphur, and phosphorus. Chemically 
pure iron may, however, be obtained by reducing the pure peroxyd of iron 
at a red-heat by a current of hydrogen gas. 

566. Compounds of Iron with Oxygen. — Iron forms three 
definite compounds with oxygen: 1. Protoxyd, FeO ; 2. Sesquioxyd, com- 
monly called the peroxyd, Fe^ ; 3. Ferric acid, Fe0 3 . Another oxyd, 
Fe 3 4 , found native in large quantities, and known as the black, or magnetic 
oxyd of iron, is by some regarded as a distinct oxyd, and by others as a com- 
pound of protoxyd and sesquioxyd. 

Questions. — What is said of iron ? Is malleable iron found in nature ? Is the iron of 
commerce pure ? How may chemically pure iron be obtained ? What are the compounds 
of iron and oxygen ? 



IRON. 361 

567. Protoxyd of Iron, F e , does not occur in nature except in 
combination. It is a powerful base, and unites with the acids to form salts 
which have a greenish color and a styptic taste — properties which are pos- 
sessed in a very marked degree by green vitriol, which is a sulphate of the 
protoxyd of iron. Protoxyd of iron may be easily obtained in the form of a 
hydrate, by dissolving pure sulphate of iron in water recently boiled and 
adding an alkali to the solution. The bulky precipitated hydrate is at first 
nearly wbite, but absorbing oxygen from the air, it soon becomes brown, and 
finally red, from its conversion into sesquioxyd. In a moist state, this hy- 
drate constitutes the most effectual antidote in poisoning by arsenic. 

568. Sesquioxyd of Iron, F e 2 3 , Peroxyd, — is found native in 
great abundance, and constitutes some of the most valuable of the ores of 
iron. It is in this state of oxydation that iron is generally found in soils and 
minerals, assuming oftentimes a deep red color (red oxyd) as in ocher, burnt 
clay, etc. The substance called rouge, crocus, or colcothar, used for polishing 
glass or metals, is this oxyd in a state of fine powder, prepared by igniting 
the sulphate of iron. 

569. Black, or Magnetic Oxyd ofIron,F e 3 04, occurs abun- 
dantly in nature, constituting the common magnetic iron ore, and the native 
loadstone, both which acquire magnetic properties from the inductive influ- 
ence of the earth. It is also the principal constituent of the scales of oxyd 
which are detached during the forging of wrought-iron. 

570. Ferric Acid, Fe03, may be formed by heating 1 part of peroxyd 
of iron with 4 parts of saltpeter to full redness for an hour, in a covered cru- 
cible. A brown mass is thus obtained — ferrate of potash — which digested 
with water yields a beautiful violet-colored solution. 

571. Ores of Iron . — The ores of iron are extremely numerous. The 
following are some of the most valuable : Piq.. 192. 

1. The magnetic, or black oxyd, which 

has a black color and a metallic luster. 

It is found in beds in the primitive 

rocks, and sometimes constitutes entire 

mountains, as the iron-mountains of 

Missouri. It is one of the richest of the 

ores of iron, and contains about 70 per 

cent, of pure iron. The superior iron 

of Sweden and Russia is prepared from 

it. The specular iron, or red iron ore, 

consists mainly of sesquioxyd of iron ; 

under this class are included the ores known as red and brown hematites, and 

bog-iron ore. Red hematite often occurs in fibrous crystallized nodules, 

forming beautiful cabinet specimens. (See Fig. 192.) All the ores of this 

Questions. — What is said of the protoxyd ? How may it be prepared ? "What is said 
•f the sesquioxyd ? What is rouge ? What is said of the black oxyd ? What of ferric 
acid ? What are the principal ores of iron ? 

16 




362 



INORGANIC CHEMISTRY. 







class yield reddish brown powders, and may thus be distinguished from the 
black oxyd ; — they contain about G3 per cent, of iron ; 3. Clay-iron stone is 
an impure carbonate of iron, mingled with varying proportions of clay, lime, 
magnesia, and manganese. This ore occurs extensively associated with coal, 
and contains about 33 per cent, of metallic iron ; it is the chief source of the 
enormous quantity of iron manufactured in Great Britain. All clays which 
are capable of yielding 20 per cent, of iron are called ores. 

572. Bi-Sulphuretof Iron, Fe %— iron pyrites,— although a very 
abundant mineral, is not used as a source of metallic iron ; it occurs in cu- 
PlG. 193. kical crystals (see Fig. 193) and fibrous 

radiated masses ; from its bright yellow color 
and metallic luster it is often mistaken for 
gold (fool's gold), but its character may be 
easily determined by the sulphurous odor 
which it evolves by heating. 

573. Protosulphate of Iron, 
F e , S 3 -{-7 HO.— Copperas ; Green Vit- 
riol. — This salt may be readily formed by dis- 
solving metallic iron in sulphuric acid, but 
for commercial purposes it is prepared on a 
very large scale by exposing iron pyrites to the action of a'r and moisture, — 
the sulphuret of iron, by the absorption of oxygen, yielding sulphuric acid 
and oxyd of iron. The salt produced is then dissolved out with water, and 
the solution allowed to crystallize. In this way it is prepared in great quan- 
tities at Stafford, Vermont. 

Copperas forms beautiful, transparent, bluish-green crystals, which effloresce 
in dry air, and become covered with brownish-white crust. In combination 
with certain astringent vegetable matters, as tannin, extract of galls, etc., it 
forms permanent black dyes, and is hence much used in the arts for dye- 
ing, and for the manufacture of inks. 

574. Iron is employed in the arts in three different states, viz., as crude, 
or cast iron, as lorought, or malleable iron, and as steel. 

575. Cast Iron, the metal obtained by smelting the ore with carbon, 
is a chemical compound of iron and carbon — a carbide, or carburet of iron, 
containing also, as impurities, small quantities of uncombined carbon and 
silicon, and generally some phosphorus, sulphur, aluminum, and calcium. It 
is fusible at a glowing white-heat, is brittle, and can neither be forged or 
welded. The proportion of carbon in different varieties of cast-iron varies, 
but in no instance does it exceed 5 per cent. The proportion of silica varies 
from 3*5 to 0*25 per cent. 

In commerce, two varieties of cast-iron are recognized, viz., white and 
gray metal. The former contains more carbon, and is harder, more brittle, 



Questions. — What are iron pyrites? "What is copperas ? How is it prepared ? What 
are its uses ? In what three conditions is iron employed in the arts '? What is cast-iron ? 
What two varieties are recognized ? What are their respective properties ? 



IRON 



363 



and more fusible than the latter. It is also characterized by a silvery white- 
ness, and a lamelar crystalline fracture. Gray metal, on the contrary, is very 
soft, dark in color, and of a granular texture ; it admits of being filed and 
drilled with ease, which white metal does not. If white iron be melted and 
allowed to cool very gradually, a portion of its carbon crystallizes out as 
graphite, and gray cast-iron is produced. The gray metal is best adapted for 
castings, and the white for the manufacture of bar iron and steel 

576. Smelting of Iron . — The operation of smelting iron, or the 
reduction of its ores to a metallic state, is ef- 
fected through the agency of the blast-fur- 
nace, which is a tall, chimney-like structure, 
constructed of stone in a conical form, and 
lined upon the interior with the most refrac- 
tory fire-brick. Its internal cavity, repre- 
sented in section in Fig. 194, resembles in 
shape a long, narrow funnel, inverted upon 
the mouth of another shorter funnel, and is 
divided into the central portion, &, called the 
shaft ; the boshes, e, or the part of the fur- 
nace sloping inward ; the crucible, t, and the 
hearth, h. The top, or mouth of the furnace 
serves both for charging it, and for the es- 
cape of gases. A steady and intense heat is 
maintained by means of strong blasts of air 
driven into the furnace by powerful blowing 
apparatus through a number of blast-pipes, 
or tuyeres, a a, at its base. The amount of 
air thus supplied exceeds, in some large furnaces, 12,000 cubic feet per min- 
ute. It was formerly the practice to use the air at ordinary temperatures 
(cold blast), but within a comparatively recent period the production of iron 
has been very greatly cheapened and increased by heating the air to a tem- 
perature of about 500° F. before it enters the furnace (hot-blast). 

At the commencement of operations, the furnace is first heated with coal 
only, for about 24 hours, in order to raise it to the proper temperature ; but 
when working regularly, it is charged alternately with coal and a mixture of 
ore and limestone broken into small pieces, until it is completely filled with 
successive layers of fuel and of ore. The ore before smelting is generally 
roasted, or heated separately, in order to expel from it water and carbonic 
acid, and render it dry and porous. The limestone added serves as flux — 
,that is, it renders the silica, clay, and other foreign matters associated with 
the ore readily fusible — forming a dark-colored glass termed " slag." As 
soon as the ore has become thoroughly ignited, its oxygen unites with the 
carbon of the fuel to form carbonic oxyd, while the metal fuses, and together 
with the slag flows down to the bottom of the furnace. Here the slag, being 

Questions. — Describe the construction of a hlast-furuace ? How is iron reduced from 
the ore ? Why is limestone used in the smelting of iron ? 




364 INORGANIC CHEMISTRY. 

the lightest, floats upon the top of the melted metal, and from time to time 
is raked off through apertures contrived for the purpose — the iron being 
drawn off by openings at a lower level. As the contents of the furnace are 
removed from below, or consumed, fresh materials are supplied from above, 
so that the process of smelting goes on uninterruptedly, day and night, for 
years, or until the furnace requires repair. The melted iron drawn off from 
the blast furnace is run into rude molds of sand, and when solidified consti- 
tutes crude cast-iron, or the pig-iron of commerce. 

577. Malleable, or Bar Iron, is cast-iron deprived of 
its carbon and other impurities. It is not fusible at a 
white heat, and may be forged and welded. 

The manufacture of bar-iron, or the purification of the crude pig-iron, is ef- 
fected by exposing cast-metal to the regulated action of oxygen at a high 
temperature, whereby the carbon, and other oxydizible impurities which it 
contains, are burnt out of it, and the iron left pure. The details of the process 
are essentially as follows : — the crude pig-iron is first remelted and suddenly 
cooled, by which it loses a part of its carbon and silica, and is rendered white, 

Fig. 195. 




crystalline, and exceedingly hard. In this state it is known as fine metal. 
Broken into fragments, it is next introduced in charges of about 500 lbs. weight, 
into a kind of reverberatory furnace, called a puddling furnace, and again 
melted. The workmen then, by means of long iron bars, stir up (puddle) the 
fused mass, and thoroughly expose it to the influence of the heated air circu- 
lating above it. (See Fig. 195.) As the operation proceeds, the metal passes 
from a liquid to a pasty condition, emits blue flames (carbonic oxyd), gradu- 
ally grows tough and less plastic, and finally becomes pulverulent. At this 
point the heat is raised to the highest intensity, and air is carefully excluded 

Questions What is malleable or bar-iron ? What is the principle of its preparation ? 

Describe the first step of the process ? What is puddling ? 



IRON. 



365 



by closing the furnace. After a time, the metal softens sufficiently to enable 
the puddler to collect it in balls (called blooms), upon the end of an iron bar, 
which are then withdrawn from the furnace, and subjected, while in a state 
of intense heat, to the action of a massive hammer, moved by machinery. A 
melted slag (silicate of the oxyd of iron) is thus forcibly squeezed out of the 
metal, and the particles of iron are brought nearer to each other. The iron is 
then fashioned into a bar, by passing it between grooved rollers ; and the bar 
thus obtained is cut into lengths, piled up in a reverberatory furnace, reheated 
and re-roiled. For the best qualities of iron, this process of doubling upon 
itself, reheating and re-rolling, is repeated several times, in order to render the 
fibers of the iron parallel to each other — an arrangement which greatly in- 
creases the tenacity of the metal. These operations, when properly per- 
formed, free the iron from all but mere traces of the impurities contained in 
the crude metal. The complete separation, however, of phosphorus and sul- 
phur, when present, is a matter of great difficulty ; and these two elements, 
above all others, are the most injurious to iron — rendering it brittle and 
rotten.* 

578. Malleable Iron Castings . — Small articles of cast-iron, such 
as stirrups, bits, door- latches, etc., may be rendered malleable in a degree, by 
closely packing them in powdered hematite (peroxyd of iron) in tight fire- 
brick cases, and 1 subjecting them to a reoT^heat, in what is called an annealing 
furnace, for a period cf time varying from six to ten days, finally" alio wing' 
them to cool slowly. In this case, the character of the iron is changed, by 
a removal of a part of its carbon, through the agency of the oxygen of the 
powdered hematite.f 

579. Steel is a chemical compound of carbon and iron — 
a carburet or carbide of iron — containing, however, a much 
less proportion of carbon than cast-iron. 

The quantity of carbon in good steel varies between Oj[_and V? per cent ; 
but steel which possesses the greatest tenacity, has been found to contain 
from 1-3 to 1'5 per cent, of carbon, and about 0-1 of silicon. 

What is called Natural Steel is 'produced directly from the best cast-iron 



* The presence in Tbar-r-on of 0-033 per cent, of sulphur, is sufficient to destroy its prop- 
erty of welding, and render it brittle when hot. Such iron is termed " hot short." Iron, 
on the contrary, which contains phosphorus, maybe readily forged and welded when hot, 
but breaks when cold ; it is accordingly known as " cold short." The discovery of a 
ready method of effectually separating these two elements from iron, is regarded as ono 
of the great problems of chemical science which yet remains unsolved. 

t Sheet-iron is bar-iron rolled while hot to the requisite degree of thinness. It is a very 
popular notion, that the so-called " Russian sheet-iron" is manufactured in Russia by a 
secret process ; but such is not the case. The iron in question is, in the first instance, a 
very pure article, rendered exeedingly tough and flexible by refining and annealing. Its 
bright, glossy surface is partially a silicate and partially an oxyd of iron, produced by pass- 
ing the hot sheet, moistened with a solution of wood-ashes, through polished steel rollers. 

Questions.— What are malleable iron castings ? What is steel ? What is the percent- 
age of carbon in steel ? How is natural steel produced ? 



366 INORGANIC CHEMISTRY. 

by exposing it, in a melted condition on the hearth of a furnace, to the action 
of a current of air ; the oxygen of the air burns off a portion of the carbon 
from the cast-iron, and steel remains. The preparation of natural steel, there- 
fore, is an intermediate stage in the conversion of cast into wrought-iron. 
Steel thus obtained is of an inferior quality, and is used for making cheap 
and coarse instruments. The best qualities of steel are obtained by a process 
called cementation, which is an operation just the reverse of that by which 
natural steel is formed. It consists in imbedding bars of the best refined mal- 
leable iron in powdered charcoal contained in large boxes of fire-brick in such 
a way that all access of air from without is entirely excluded. The boxes 
are then subjected, in a furnace, to a most intense heat, for a period varying 
from five to ten days, during which time the carbon of the charcoal completely 
penetrates the mass of the iron, and converts it into steel. The steeL when 
withdrawn, has a peculiar, rough, blistered appearance, and is hence known 
as blistered steel. Small bars of blistered steel, made into faggots and welded 
together, at a high temperature, under a tilting, or trip hammer, forms " tilted 
steel;" this, broken up, reheated, and re-welded, forms u shear steel" so called, 
because it was originally thus prepared for making shears to dress woollen 
cloth. The quality of the steel is greatly improved by these successive pro- 
cesses of reheating and re-hammering. Cast steel is prepared by melting 
blistered steel, casting it into ingots, and then drawing it into bars under the 
hammer ; it is the most perfect variety of steel, and is employed for all fine 
cutlery. 

Case-hardening . — It is sometimes desirable to convert articles 
manufactured from soft iron superficially into steel; this is termed case- 
hardening, and is usually performed by heating them for a short time in 
contact with powdered charcoal, or sprinkling their surfaces when red-hot 
with powdered ferrocyanide of potassium^ 

580. The chemical changes which take place in the conversion of bar-iron 
into steel are obscure, and it is somewhat doubtful whether we yet fully un- 
derstand the exact composition of steel. The most recent researches seem to 
indicate that nitrogen is a constituent of all steel, and that its presence, to* 
gether with carbon, is essential to its formation. The finest steel known, 
called " Wootz, is produced in a very rude way by the natives of India, and is 
used for the manufacture of the celebrated sword-blades of the East. The 
most experienced English manufacturers are unable, with all their resources, 
to produce steel of an equal quality, and its peculiar excellence has been at- 
tributed by Professor Faraday to the presence in its composition of a small 
quantity of aluminum ^ 

* Some authorities have supposed that carbon is contained in steel in the form of the 
diamond, since it seems almost impossible to refer the great differences which exist be- 
tween cast-iron and steel to merely a minute variation of the proportions of the combined 

Questions How is the best steel obtained ? What are the different varieties of steel ? 

What is cast-steel ? What is case-hardening ? What is said of our knowledge of the 
formation and composition of steel ? 



MANGANESE — CHROMIUM. 367 

581. Properties of Steel,— Steel is less fusible than cast-iron, / 
and more so than bar-iron. Its most remarkable property consists in its / 
power of assuming a hardness scarcely inferior to that of the diamond by 
heating to redness and then suddenly cooling by immersion in cold water ; 
by this treatment it is also rendered . extremely brittle and almost perfectly 
elastic. By reheating the steel and allowing it to cool slowly, it again be- 
comes nearly as soft as ordinary iron, and between these two extremes any 
required degree of hardness may be attained. In working steel, the articles 
are first finished in a soft state, and afterward hardened ; they are then tem- 
pered, or raised to such a temperature as is requisite to give them the degree 
of softness and elasticity required. The workman easily estimates this tem- 
perature by observing the color of the thin film of oxyd which appears upon 
the surface. Thus, a light straw color indicates the degree of heat requi- 
site for tempering razors; a deep yellow, that suitable for scissors, pen- 
knives, etc. ; while sword-blades, watch-springs, and instruments demanding 
great elasticity, must be exposed to a much higher degree of heat, or until 
their surfaces acquire a deep blue color. These various changes in the color 
of steel may be illustrated by heating a polished steel knitting-needle in tho 
flame of a spirit-lamp. 



<t 



SECTION II. 

MANGANESE AND CHROMIUM. 

582. Manganese .— -Equivalent, 27 '6 ; Symbol, Mn ; Spe- 
cific gravity, 8. — Metallic manganese is a grayish-white 
metal, resembling some varieties of cast-iron. 

It is extremely brittle, and so hard that it is not scratched by a file ; a 
fragment set at a sharp angle may be even substituted in the place of the 
diamond for cutting glass. It is susceptible of a very high polish, and at or- 
dinary temperatures in the air is not readily oxydized. It dissolves easily 
in acids. No practical application has ever been made of this metal, and 
previous to its investigation by Brunner in 1857, very erroneous ideas of its 
properties were generally entertained. It is now believed to possess a high 
economic value, especially as an element of certain alloys. Its preparation 
is, however, difficult. 

Manganese is not found in nature as a metal, but as an oxyd it is very 
widely diffused in the mineral kingdom. Traces of it are very frequently 



carbon. In accordance with, tliis view, a theory has been proposed, that the fine cutting 
properties of a steel blade, are due to a minute form of diamond imbedded in the edge ; 
and that the benefit of dipping a razor into hot -water before using is owing to the circum- 
stance that the metal is thereby expanded, forcing the sharp edges of the embedded car- 
bon crystals into such positions, that they cut with greater facility. 

Questions. — What are the properties of steel ? What is understood by the tempering 
of steel ? What is the appearance of metallic manganese ? What are its properties ? 
What is said of its distribution in nature ? 



368 INORGANIC CHEMISTRY. 

found in the ashes of plants, and in river and lake waters. The dark, metal- 
lic-like discoloration which may be often noticed on stones and pebbles in 
the beds of streams flowing over igneous rocks, is due in great part to a 
coating of oxyd of manganese deposited from the water. The most impor- 
tant and valuable ore of manganese is the black oxyd, also known as the 
peroxyd, or binoxyd, Mn0 2 . It is found abundantly at Bennington, Yermont, 
and in many other localities in the United States. 

Seven different oxyds of manganese are described, the two highest of which 
possess acid properties, and are termed manganic and permanganic acids. 
Manganic acid is known only in combination with potash, with which it forms 
a salt — manganate of potash — possessing some very curious properties. It is 
best prepared by intimately mixing 4 parts of finely-powdered peroxyd of 
manganese with 3£ parts of chlorate of potash ; 5 parts of hydrate of potash 
dissolved in a small quantity of water, are then added to the mixture, which 
evaporated to dryness and heated to dull redness for an hour in an earthen 
crucible, yields a dark green mass. This dissolved in water, gives at first 
an emerald-green solution, but the color almost immediately and successively 
changes to dark-green, blue, purple, and finally to crimson. These changes 
of color are occasioned by a decomposition of manganate of potash, which is 
hence often called chameleon mineral ; the final red color retained by the so- 
lution is due to the formation of permanganic acid, which is comparatively a 
stable compound. 

The salts of manganese are characterized by a delicate rose-color, which is 
especially noticeable in crystals of the sulphate. The chief uses of the com- 
pounds of manganese are chemical, the black oxyd being extensively employed 
to decompose muriatic acid, and furnish chlorine (§ 350) ; it likewise supplies 
the chemist with his cheapest source of oxygen, and is used as a coloring/ 
material in the manufacture of glass and enamels. — Miller. </ */^" 

583. Chromium,— Equivalent, 26*4 ; Symbol, Cr. — Chro- 
mium is found only as an oxyd in nature, and although 
abundant in some localities, is very sparingly distributed 
over the earth. The metal itself, which is obtained with 
difficulty, is grayish-white, brittle, and is extremely hard; 
it also resists the action of the strongest acids. 

The most abundant ore of chromium, is a compound of protoxyd of iron 
and sesquioxyd of chromium, — known as " chrome iron." It is found more 
abundantly in the United States than elsewhere, especially in the vicinity 
of Baltimore, and at Lancaster, in Pennsylvania. 

Almost all the compounds of chromium are characterized by very beautiful 
colors, and are hence highly valued in the arts as materials for paints, for 

Questions. — What is its principal ore? What is said of its compounds with oxygen? 
What peculiar properties does the manganate of potash possess? What are the proper- 
ties of chromium ? What is its principal ore ? For what are the compounds of chromium 
remarkable ? 



MANGANESE — CHROMIUM. 369 

dyeing fabrics, and for coloring glass, porcelain, enamels, etc. Oxyd of 
chromium is the coloring ingredient of the emerald, of the green varieties of 
serpentine, and probably also of the ruby. 

Chromium is prepared for use in the arts by fusing the pulverized ore, 
chrome iron, with nitrate of potash (saltpeter) ; by this treatment the chro- 
mium absorbs oxygen and becomes converted into an acid — chromic acid — 
which unites with the potash of the niter to form a yellow salt, the chromate 
of potash, KO,Cr03. By adding sulphuric acid to a solution of chromate 
of potash, we remove one half the base and form a new salt — bi-chromate 
of potash, KO, 2Cr0 3 — which crystallizes in beautiful red tables, and furnishes 
the source from whence most of the other compounds of chromium are pre- 
pared. It is also in the- form of this salt that chromium is best known as an 
article of commerce. 

584. Chromate of Lead, PbO,Cr0 3 . — Chrome Yellow. — By 
adding a solution of bi-chromate of potash to a solution of acetate of lead, we 
obtain a beautiful yellow precipitate of chromate of lead ; this, washed and 
dried, constitutes the well-known pigment, chrome yellow. By mixing chrome 
yellow with white substances, such as chalk, clay, etc., numerous other shades 
of yellow are obtained, as Paris yellow, king's yellow, etc. ; but by mixing it 
with Prussian' blue, a variety of cheap green pigments are formed, as Naples 
green, olive green, etc. 

585. Chromic Acid, Cr0 3 , is readily prepared by mixing 4 mea- 
sures of a cold saturated solution of bi-chromate of potash with 5 of oil of vit- 
riol; as the liquid cools, chromic acid is deposited in the form of beautiful 
crimson needles. The mother liquor is then poured off, and the crystals 
allowed to dry on a porous brick, closely covered with a bell glass ; since they 
decompose instantly by contact with organic matter. "When chromic acid is 
brought in contact with alcohol or ether, it imparts to these substances a por- 
tion of its oxyyen, and the intensity of the chemical action occasioned, pro- 
duces an immediate ignition. This may be illustrated by projecting a small 
quantity of chromic acid upon a little alcohol or ether contained in a tum- 
bler. 

If we mix in a small mortar as much chromic acid as can be taken Upon 
the point of a knife, with about one quarter as much of powdered camphor 
(without pressing upon it strongly), and then let fall into the mortar a few 
drops of alcohol from a considerable height, instantaneous ignition and de- 
flagration ensues — like the burning of gunpowder. The residue in the mortar, 
after the decomposition, is sesquioxyd of chromium, which presents the appear- 
ance of an elegant green, mossy vegetation. — Stockiiart. 

Questions. — Hcrw is it prepared for use in the arts? What is the composition of bi- 
chromate of potash ? What is chrome yellow ? How is chromic acid prepared ? What 
are its properties ? 

16* 



370 INORGANIC CHEMISTRY. 



SECTION III. 

COBALT AND NICKEL. 

586. Cobalt. — Equivalent, 29*5, Symbol, Co. — Cobalt is 
a reddish-gray metal, which is never found in nature in a 
metallic state, except as a constituent, in small propor- 
tions, of meteoric iron. 

Oxyd of cobalt is remarkable for the magnificent blue color it communicates 
to glass, and also to porcelain. This may be illustrated by moistening a small 
bead of borax glass with a solution of nitrate of cobalt, and then fusing it in 
the flame of a blow-pipe. The substance called smalt is a glass, colored blue 
by oxyd of cobalt, and then finely pulverized ; it was formerly much used as 
a pigment, especially in the manufacture of blue writing-paper ; but is now 
almost entirely superseded by the cheaper ultramarine. 

587. Sympathetic Inks . — The chloride of cobalt, CoCl, is easily ob- 
tained by dissolving oxyd of cobalt in hydrochloric acid ; the solution, evapor- 
ated to small bulk, yields ruby-red crystals, which are freely soluble in water. 
The liquid resulting from their aqueous solution, is of a deep-blue color when 
concentrated, but when diluted, is pink. In this latter condition it may be 
• used as a sympathetic ink : characters written on paper with it are invisible, 
from their paleness of color, until the salt has been rendered anhydrous by 
exposure to heat, when the letters appear blue. When the paper is laid 
aside, moisture is again absorbed by it, and the writing once more disappears. 

588. Nickel.— Equivalent, 29*6 ; Symbol, Ni.— Nickel is 
a brilliant, silver-white metal, extremely ductile, and more 
fusible than iron. It occurs in nature associated chiefly 
with arsenic, sulphur, and cobak ; but its ores are by no 
means abundant. It is almost always found native in me- 
teoric iron, sometimes in a proportion of 10 per cent. 

The salts of nickel are of a delicate green color, both when in a solid state 
and when in solution. 

The chief use of nickel is in the manufacture of German silver, which is a 
white, malleable alloy, consisting, in 100 parts, of 51 parts of copper, 30*6 of 
zinc, and 18 "4 of nickel — the latter element imparting to the alloy, when pol- 
ished, a silver-like appearance. 

589. General Properties of Cobalt and Nickel. — These 
two metals are especially remarkable from the circumstance, that they almost 

Qttestions.— What is said of metallic cobalt ? What are the characteristics of oxyd 
of cobalt? What is smalt? What is sympathetic ink ? What is said of the properties 
and distribution of nickel ? What of its salts ? What of its uses ? What is German 
silver ? In what respects do cobalt and nickel resemble each other ? 






I 



ZINC . — C A D M I U M . 371 

always occur associated together in nature, have nearly the same chemical 
equivalent, and agree very closely in their chemical properties. They are 
also the only metals beside iron which are readily susceptible of magnetism. 

SECTION IV. 

ZINC AND CADMIUM 

590. Zinc. — Equivalent, 32*5; symbol, Zn ; specific 
gravity, &8 to 7.— Zinc is not found native, but its ores 
are somewhat abundant. 

The most important of its ores are the carbonate of zinc, called calamine ; 
the . red-oxyd of zinc, found in great purity and quantity at Sterling, New 
Jersey ; and a sulphide of zinc, called Mende — the latter being usually associ- 
ated with ores of laad. ' 

591. Properties . — Zinc is a hard, bluish- white. metal, which exhibits 
a crystalline fracture when broken. It is brittle at ordinary temperatures, 
but between 200° and 300° F. acquires considerable malleability and duc- 
tility, and may be rolled and wrought with ease ; it is a very singular fact 
that zinc so treated retains its malleability when cold, and it is in this way 
that the ordinary sheet-zinc of commerce is manufactured. - At a temperature 
of 400° it again becomes so brittle as to admit of being pulverized in a mor- 
tar. At 770° it melts, and at a bright red heat it is volatilized. If its vapor 
be broughtTh" contact with air, it burns with a splendid green light, and is 
converted into oxyd, which falls in copious white flakes, anciently called 
"philosopher's wool." Zinc, when exposed to a moist atmosphere, soon 
tarnishes, and becomes covered with a thin film of oxyd, which protects the 
metal beneath from any further change. This property renders zinc valuable 
for a great variety of economic purposes. 

By reason of the volatility of zinc at high temperatures, it is reduced from its 
ores by a process of distillation rather than smelting. This is effected by heat- 
ing a mixture of pulverized ore and coal in earthen retorts, and condensing 
the evolved vapors over water, # or in receivers from whence free access of air 
is excluded. The zinc of commerce always contains impurities, generally 
iron and lead, and sometimes arsenic, 

592. Galvanized Iron is sheet-iron coated with zinc. It is prepared as 
follows : the iron is first immersed in dilute sulphuric acid, to remove all scale 
or oxyd from its surface, and then plunged into a bath of molten zinc, cov- 
ered with sal-ammoniac. The use of the latter substance is to dissolve off 
any adhering film of oxyd from the iron, as a complete union of the two 
metals will not occur unless the surface of the iron is chemically clean. The 
thin coating of zinc which adheres to the iron renders the latter metal nega- 
tively electric, and prevents its oxydation or rusting. (§ 247.) 

Qtjebtioxb. — What is said of the distribution and ores of zinc ? What are the proper- 
ties of zinc ? How is zinc reduced from its ores ? What is galvanized iron ? 



372 



INOKGANIC CHEMISTRY. 



593. Oxyd of Zinc, ZnO . — Zinc White. — Zinc forms only one com- 
pound with oxygen, which, when pure, is a white powder. Mixed with 
drying oils, it is much employed as a white paint, under the name of zinc- 
white, as a substitute for white lead ; it wants, however, tho opacity and dead 
whiteness for which white lead is so much valued ; but has the advantage 
of not blackening by the action of sulphuretted hydrogen, and of not being 
deleterious to the health of the workmen.* 

Sulphate of zinc, ZnO,S0 3 , constitutes the white vitriol of commerce; it 
used medicinally in small doses, and also in the operations of calico printing. 
.' The salts of zinc are colorless, and act powerfully and rapidly as emetics. 

594. Cadmium, Cd,isa white metal, resembling tin in appearance, 
but allied to zinc in its properties. It is usually found in very small quanti- 
ties accompanying the ores of zinc, and has no practical value in the arts. 



I ! 



SECTION Y. 



LEAD AND TIN 



595. Le ad.- 



FiG. 196. 



-Equivalent, 103*5; Symbol, Pb (Plumbum); Specific gravity, 
11 '44. — Lead is rarely found native, but its ores are most abun- 
dant. Almost all the lead of commerce is obtained from galena, 
or the sulphide of lead, PbS, an ore which occurs in bound- 
less profusion in the United States, especially in Missouri. 
The reduction of the metal is easily effected by crushing the 
ore and subjecting it to a moderate heat in a reverberatory 
furnace. Galena always contains a proportion of silver, 
which is sometimes so abundant that the ore is worked for 
this metal rather than for the lead. "When the galena oc- 
curs in bold, well-characterized cubes (see Fig. 196), the contained lead is 




* Zinc-white is at present extensively manufactured from the red zinc ore found at 
Sterling, New Jersey, by an exceedingly interesting and simple process. The ore, pul- 
■yjiizcd and mixed with coal, is heated in large oven-shaped retorts of brick, to each of 
which a wide pipe of sheet-iron is fitted ; these extend through the furnace wall and con- 
nect with a very large horizontal tube, through which a current of air is kept moving by 
the revolution of a fan-wheel. The current thus formed flows first through the retorts, 
and burns the vapor of zinc to oxyd ; which is immediatel> transported by the draft of 
air through the continuation of the tube to a chamber, where it falls as delicate powder. 

Oxyd of zinc, in combination with chloride of zinc, has recently been applied to pro- 
ducing a lustrous hard finish to the walls of rooms, in the place of plaster of Paris. A 
coat of oxyd of zinc mixed with size, and made up like a wash, is first laid on the wall, 
ceiling, or wainscot, and over that a coat of chloride of zinc applied, being prepared in 
the same way as the first wash. The oxyd and chloride effect an immediate combination, 
and form a kind of cement, smooth and polished as glass. 



Questions. — "What is said of oxyd of zinc ? How is it prepared ? "What is said of sul- 
phate of zinc? What of cadmium? What is said of the distribution of lead? What i» 
galena? What is a usual constituent of this ore? 



LEAD. — TIN. 373 

usually nearly pure ; but a mineral which will yield 0-36 per cent, of silver, 
or 120 ounces to the ton, is considered extremely rich.* 

596. Properties . — Lead is a soft, bluish-gray metal, which may be 
rolled into tolerably thin sheets, or drawn into wire ; its tenacity, however, is 
very feeble. It fuses at 620° P., and contracts considerably at the moment 
of its solidification, which circumstance renders it unsuitable for castings. At 
a temperature above red-heat it is somewhat volatile 

The surface of a piece of lead, when freshly cut, presents a high metallic 
luster, but it soon tarnishes by exposure to the air, owing to the formation of 
a thin, closely-adherent film of oxyd, which protects the metal from further 
change. In a perfectly dry atmosphere, lead undergoes no alteration, and 
even when sealed up in a vessel of pUre water, free from air, the metal will 
retain its brilliancy for an indefinite period ; but if it be exposed to the united 
action of air and -pure water, it is subject to a powerful corrosion. — Miller. 

597. Lead, when taken into the system in any soluble form, is a dangerous 
poison ; its effects, moreover, do not generally manifest themselves immedi- 
ately, but the poison accumulates, and produces, often after the lapse of years, 
a number of different and distressing forms of disease, such as colic, paralysis, 
etc. The action of water on lead is, therefore, a matter of great importance 
in a sanitary point of view, since this metal is extensively employed in cis- 
terns and pipes, for the storage and supply of water. 

The action of different waters on lead varies considerably. "Waters which 
are very pure and highly aerated — waters which contain nitrates, chlorides, or 
organic matter, as those flowing from the vicinity of barn-yards, manure 
heaps, or from swamps and fields, all dissolve lead from the pipes through 
which they pass ; and the constant use of such waters, in the process of time, 
will introduce sufficient lead into the system to produce disease. Waters, on 
the other hand, which contain sulphates, carbonates, and phosphates, exert 
but comparatively little action on lead. Bi-carbonate of lime is especially re- 
markable for the preservative influence which it exerts ; and as this salt is a 
very common impurity in water, few spring waters act on lead to a dangerous 
extent. In these cases, a film of insoluble carbonate, sulphate, or phos- 
phate of lead, is formed upon the surface of the pipe, and all further corrosion 
prevented. Rain-water, as collected from the roofs of houses, is for the most 
part sufficiently impure, especially in cities, to prevent its action on lead. So 
general, however, is the action of water upon lead, that it is rare to find any 



* So small a quantity of silver as three or four ounces to a ton of lead, may be ex- 
tracted profitably by a process devised by Mr. Pattinson, of England. It consists in 
melting the argentiferous lead, and allowing it to cool slowly. Under these circumstances, 
the lead tends to separate in the form of crystals of pure metal, before the alloy of silver 
has been cooled sufficiently to solidify. By a careful regulation of temperature, the great 
mass of the lead may, therefore, be removed mechanically, leaving the silver concentrated 
in a small bulk of alloy. 

Questions. — What are the properties of lead ? What changes does lead undergo in the 
air? What is said of the poisonous influence of lead? What of the action of water on 
lead ? What salts arrest the action of water on lead ? How do they effect this? 



374 



INORGANIC CHEMISTRY. 



water that has been kept in contact with this metal for a considerable period, 
which does not contain some traces of it. Stone and wooden cisterns, and 
tin, iron, or wood pipes, are therefore, greatly to be preferred to lead. "Where 
lead service-pipes are used, it is always advisable to allow the water to run 
for some time before using. 

598. Oxyds of Lead .—Four distinct oxyds of lead are recognized, the 
most important of which are the protoxyd, PbO, and the peroxyd, Pb0 2 . 

Protoxyd of Lead, Litharge, Massicot, PbO, is a yellow powder, 
usually obtained on a large scale, by the oxydation of molten lead in a cur- 
rent of air. Its production may be illustrated by fusing a small piece of lead 
on charcoal, before the exterior flame of a blow-pipe. The melted lead oxyd- 
ating, is at first converted into a grayish powder — a mixture of oxyd of lead 
and metallic lead — but by continued blowing, the gray color is changed into a 
brilliant yellow —litharge. This oxyd of lead is a powerful base, and is ex- 
tensively used in the arts, especially in the glazing of pottery and the manu- 
facture of flint glas3. United with fatty acids it forms insoluble soaps (the 
well-known diachylon, or lead plaster) ; and boiled with linseed-oil, it consti- 
tutes a varnish much used by cabinet-makers. 

R e d - L e a d , or M i n i u jr. , 2 P b . P b 2 , is a compound of prot- 
oxyd and peroxyd of lead. It is formed by exposing protoxyd of lead, for a 
long time, to the action of air, at a temperature below fusing. It possesses a 
brilliant red color, and is much used in the arts in the manufacture of glass, 
as a pigment, and for the coloring of red sealing wax and of paper. 

599. Carbonate of Lead, P b , C 2 . — White-Lead. — This salt 
occurs in nature, but is prepared artificially, in immense quantities, for use as 
a paint. Pure carbonate of lead is a soft, white powder, insoluble in water, 
but easily dissolved by dilute nitric or acetic acids. 

Two methods are in use for making white lead. One of these consists in 
dissolving litharge in acetic acid, and precipitating the lead as carbonate, by a 
current of carbonic acid gas. The best white lead is, however, made by a pro- 
• Pig. 197. cess known as the "Dutch method." A great number of 

small earthen pots are partially filled with weak vinegar, 
and a thin sheet of lead, coiled in a spiral, placed in 
each. (See Pig. 197.) The pots are then each covered 
with a plate of lead, and arranged in rows and tiers, one 
above the other, to the height of 15 or 20 feet, and the 
whole finally covered with decomposing stable manure or 
spent tan. After the lapse of several months, the rolls 
of lead are found to be mostly or entirely converted 
into a pure white carbonate, which only requires washing and grinding to fit 
it for immediate use. The theory of this curious process is as follows : the 




Questions. — What oxyds of lead are there? By what names is protoxyd of lead 
known? How is ib prepared? What are its properties and uses? What is red-lead? 
What other name is applied to it? What are its uses ? What is white-lead? How is it 
prepared ? 



LEAD. — TIN. 375 

heat of the decomposing dung, etc., volatilizes a portion of the vinegar, aa 
acetic acid, and under the influence of air and acid fumes, a crust of acetate 
of lead is formed upon the surface of the metal. The carbonic acid, generated 
from the slow decay and decomposition of the materials of the hot-bed, readily 
converts this salt into carbonate of lead, leaving the acetic acid free to com- 
bine with an additional portion of lead, which is, in turn, again decomposed ; 
and this action is repeated until the whole of the lead is converted into a car- 
bonate. White lead is largely adulterated with sulphate of baryta, but the 
fraud may be easily detected by digesting a sample in nitric or acetic acids, 
when the baryta will remain undissolved. 

600. The most ready solvent for lead is nitric acid; dilute sulphuric and 
hydrochloric acids not acting upon it to any great extent. 

The presence of lead in solution may be easily detected by any of the fol- 
lowing tests : with sulphuric acid it forms a white, insoluble precipitate — sul- 
phate of lead; with sulphuretted hydrogen, a 
black sulphide, visible, when the quantity of lead 
present is very minute, only after a little time ; 
and with solutions of bi-chromate of potash or 
iodide of potassium, yellow precipitates. 

Zinc precipitates lead from its solution by vol- 
taic action, in the form of crystalline metallic 
particles, forming what is known as the lead- 
tree. (Fig. 198. § 255.) 

In case of poisoning by a dose of soluble lead 
salts, the best antidote is Epsom salts (sulphate 
of magnesia), with which the lead forms an in- ' 
soluble and inert sulphate. This remedy, how- 
ever, is ineffectual in the more usual forms of lead-poisoning, in which the 
metal is introduced into the system in minute quantities, in water or in articles 
of diet. 

601. Alloys of Lead . — The alloys of lead are numerous and impor- 
tant. Shot is an alloy of lead, with a small proportion of arsenic, which 
hardens it, and facilitates its separation into globules. In the manufacture 
of shot, the lead is melted at the top of high towers built for the purpose, 
and poured into a vessel perforated in the bottom with numerous small holes. 
The lead, in running through, is separated into drops, which falling through 
the height of the tower, become spherical, and cool before reaching a reser- 
voir of water placed for their reception at the base of the tower. For the 
manufacture of the largest sized shot, a tower of at least 150 feet high is 
required. Shot are proved, and the different sizes separated, by rolling them 
down an inclined board. Those which are irregular in shape, roll off at the 
sides, or stop, while the perfectly spherical ones continue in a straight course. 



Question's. — "What is the most ready solvent of lead ? How may the presence of lead 
in solution be detected ? What are antidotes to lead-poisoning ? How are shot manufac- 
tured ? What is their composition ? How are shot proved ? 







376 



INORGANIC CHEMISTRY. 



Type-metal is an alloy of 3 parts lead and 1 of antimony. This alloy is suffi- 
ciently fusible to allow of its being readily cast, and it expands at the mo- 
ment of solidification, and copies the mold accurately. Solder is an alloy of 
lead and tin. 

602. Tin, — Equivalent, 59; Symbol, Sn (Stannura) ; 
Specific gravity, 7'29. — Tin occurs in nature usually as an 
oxyd, but sometimes as a sulphide. 

Its ores are very sparingly distributed over the earth — the most important 
tin-mines being those of Cornwall, England, and Malacca, in Southern Asia. 
It is also mined to a limited extent in Germany, and in a few localities in 
Mexico and South America. It has hitherto only been discovered in one 
locality in the United States, at Jackson, N. H., in very small quantities. 

Tin of two qualities, as regards purity, is recognized in commerce, viz., 
" block" or " bar" tin, and " grain" tin : the latter being a refined metal. 

603. Properties , — The properties which characterize tin and render 
it valuable in the arts, are its malleability, fusibility, softness, silver-like color 
and luster, and especially its slight affinity for oxygen, which enables it to 
retain its brilliancy at ordinary temperatures, in the presence of air and moist- 
ure. Tin melts at 442° F. If heated above this point it is not sensibly 
volatilized, but becomes rapidly oxydized, and burns with a brilliant white 
light. When a bar of metallic tin is bent backward and forward, it has a 
peculiar creaking or crackling sound, which is termed the ''tin cry;" this 
is due to the crystalline texture cf the tin, the crystals moving upon each 
other. Tin is almost insoluble in dilute sulphuric acid, and dissolves slowly 
in hydrochloric acid. Nitric acid acts upon it with great violence, not dis- 
solving the metal, but converting it into a white powder, the binoxyd of tin. 
This reaction may be easily illustrated by pouring dilute nitric acid upon a 
little tin-foil in a porcelain dish. The binoxyd of tin thus formed, when ren- 
dered anhydrous by ignition, constitutes the putty powder used for polishing 
glass, and for the manufacture of enamels. 

604. "With oxygen tin unites to form several oxyds, the principal of which 
are the protoxyd, SnO, and the peroxyd or binoxyd, SnOs. This last oxyd 
in its hydrated condition, has the character of an acid, and is then known 
as stannic acid, Sn0 2 ,HO. Tin also unites with chlorine to form two chlor- 
ides, the protochlorido, SnCl, and the perchloride, SnCl2. The last-named 
chloride is an old and very curious compound, which was formerly called the 
" fuming liquor of Libavius." It is a dense, fuming liquid, prepared by ex- 
posing melted tin to the action of dry chlorine. A preparation of bi-chloride 
of tin is extensively used in dyeing as a mordant. A M-sulphuret of tin, SnS*, 
formed by exposing to a low red heat in a glass flask a mixture of 12 parts 



Questions.— What is type-metal? "What is solder? "What is said of the occurrence 
and distribution of tin ? What two qualities of tin are known in commerce ? What are 
the characteristic properties of tin ? What is " tin-cry ?" What is the action of acids 
upon tin ? What is putty powder ? What are the principal oxyds of tin ? What is said 
of the chlorides of tin ? What is the composition of bronze powders ? 



COPPER . — B ISMUTH. 377 

tin, 6 mercury, 6 sal-ammoniac, and T flowers of sulphur, is of a brilliant 
gold color, and is known as mosaic gold. It constitutes the well-known 
bronze powders used in printing and in the manufacture of paper-hangings. 

605. The useful applications of metallic tin are very numerous. Tin-plate, 
of which ordinary articles of tin-ware are made, is sheet-iron superficially 
coated with tin. It is prepared by first rendering the surface of the iron 
chemically clean by the action of acids, and then immersing the sheet-metal 
for a considerable length of time in a bath of molten tin ; the union of the two 
metals, thus effected, is not a case of simple adhesion, but the tin forms with 
the iron an alloy. Britannia-metal, which is much used for the manufacture of 
tea-pots and cheap spoons, consists of equal parts of tin, brass, antimony, and 
bismuth. Pewter of the best quality, consists of 4 parts tin ar.d 1 of lead. 
Ordinary brass pins are tinned, or whitened, by boiling them in a vessel con- 
taining tin in a finely-divided state, and a solution of cream of tartar in water. 
The acid of the cream of tartar effects a solution of some of the tin in the 
first instance, which on longer boiling separates as a metal upon the more 
electro-positive brass. 

SECTION YI. 

COPPER AND BISMUTH. 

606. Copper. — Equivalent, 31-Y ; Symbol, Cu (Cuprum) ; Specific gravity, 
8 '9. — Copper is frequently found native, generally in small crystals, but some- 
times in immense masses, as in the mines on Lake Superior. Its ores, also, 
are numerous and abundant — the most important being, the sulphurets of 
copper, and the red oxyd. Carbonate of copper, constituting the beautiful 
green mineral malachite, is also found in sufficient abundance in some locali~ 
ties to admit of working — especially inJ3j_bexia r -Ea_stern Africa, etc. 

601. Properties . — Copper is one of the metals which has been longest 
known to man, and was extensively used long before the working of iron 
was understood. It is moderately hard, tenacious, ductile, and malleable, 
and is the only metal, with the exception of titanium, which has a red color. 
Copper requires a high degree of temperature for fusion (1990° P.), and when 
exposed to an intense heat is somewhat volatile — its vapor burning with a 
green flame. It is one of the best conductors" of heat and electricity. 

At ordinary temperatures, in a dry atmosphere, copper remains unchanged, 
but when exposed to a moist air it quickly tarnishes, and ultimately becomes 
covered with a strongly-adherent green crust, consisting chiefly of carbonate. 
Pure water has little or no action upon copper, but in sea-water, or solutions 
of the chlorides, it is gradually corroded. The corrosion and waste of the 
copper sheathing of ships is due chiefly to the oxygen contained in sea- water, 

Questions. — What is tin-plate ? "What is Britannia-metal ? What is pewter ? How 
are pins whitened ? What is said of the occurrence of copper in nature ? What are its 
chief properties? What is the durability of copper in various situations ? What occa- 
sions the corrosion of copper sheathing ? 



378 



INORGANIC CHEMISTRY. 



Fig. 199. 



and to the friction of the water ; the corrosion being greatest at those points 
where the bubbles of air inclosed in the water, by the surging at the bow, 
rise to the surface and break against the bottom of the vessel. Corrosion of 
a ship's sheathing is also slow in rnid-ocean compared to what it is at the 
mouths of tropical rivers, or in harbors, where the water is filled with par- 
ticles of organic matter in a state of decomposition. 

60S. The most ready solvent of copper is nitric acid. (§ 344.) Many of 
the weak vegetable acids also attack metallic copper, but dilute sulphuric and 
hydrochloric acids have scarcely any action upon it. , 

GO 9. The two principal oxyds of copper are the protoxyd, or black oxyd, 
CuO, and the suboxyd, or red oxyd, Cu 2 0. 

610. Protoxyd of Copper is the basis of all the ordinary salts of 
copper. It is prepared by heating metallic copper to redness in a current of 
air, and then suddenly quenching it in cold water ; or more conveniently by 
decomposing the nitrate of copper by heating it to redness — the product in 
the first instance being black scales, and in the last a dense black powder. 
It may also be obtained as a hydrate of light blue color by the addition of 
caustic potash to a solution of any of its salts, (as blue vitriol). Protoxyd of 
copper is a compound of considerable importance in chemistry and the arts ; 
when mixed with organic substances, and heated, it gives up all its oxygen, 

and is hence much used to effect the 
complete combustion of these bodies in 
a process by which their elementary 
composition is determined; it is also 
used for imparting to glass and porcelain 
^ a beautiful green color. 
, =iS 8 Suboxyd of copper is found native, 
and may be prepared by heating a mix- 
ture of 5 parts of black oxyd and 4 parts 
of fine copper filings in a covered crucible ; the red coating which is formed 
when metallic copper (as a cent, for example, see Fig. 199) is slightly heated 
and suddenly cooled, is also suboxyd of copper. Its principal industrial 
value is for imparting to glass a beautiful ruby or purple color. 

611. Sulphate of Copper, Blue vitriol, CuO,S03, is one of the most 
important of the salts of copper, and is formed by heating metallic copper 
with concentrated sulphuric acid. It crystallizes in beautiful blue crystals, 
and is soluble in 4 parts of cold and 2 of boiling water. Large quantities of 
this salt are used in calico-printings in the preparation of most of the other 
salts of copper, and as an agent for exciting galvanic batteries. Wood steeped 
in a solution of sulphate of copper is protected against dry-rot, and a wash 
of it on the wood-work of cellars is highly serviceable in preventing the 
formation of mold. Animal substances thoroughly imbued with it and then 
dried, remain unaltered. 

Questions. — What is the most ready solvent of copper ? What are the two principal 
oxyds of copper? What is said of protoxyd of copper? What of suboxyd of copper ? 
What is the composition of blue vitriol ? What are its uses and properties ? 




COPPER . — B I S M U T H . 379 

612. Nitrate of Copper, C u , N 5 , is a beautiful blue, efflor- 
escent salt, formed by dissolving metallic copper in nitric acid. It is highly- 
corrosive, and easily decomposed. Its tendency to decomposition may be il- 
lustrated by closely enveloping a few moist crystals of nitrate of copper in 
tin-foil, and placing the parcel upon a porcelain dish ; the affinity of the tin 
for the nitric acid in a short time occasions intense chemical action, accom- 
panied by the phenomenon of ignition ; a paper also, moistened with a strong 
solution of this salt, cannot bo rapidly dried without taking fire from the de- 
composition of the nitric acid. 

613. Verdigris . — Sub- Acetate of Copper. — Yerdigris is a salt cf acetic 
acid (the acid of vinegar) and oxyd of copper. It may be formed experi- 
mentally by moistening from time to time a copper coin with vinegar, which 
occasions the production of a green coating. It is prepared on a large scale, 
either directly from copper and vinegar (green verdigris), or indirectly by 
spreading the refuse of pressed grapes upon plates of copper exposed to 
the air ; in this latter case the juice adhering to the mash gradually changes 
to vinegar, and forms blue, or French verdigris. This salt is much used in 
the aits as a pigment. 

614. Characteristics of the Salts of Copper. — Most cf 
the salts of copper have a blue or green color, and nearly all are soluble in 
water. They are distinguished by a nauseating metallic taste, and when 
taken internally act as deadly poisons, producing violent vomiting, followed 
by exhaustion and death. Black oxyd of copper is soluble in oils and fats, 
so that greasy matters boiled in an copper saucepan which is not kept bright, 
are liable to become impregnated with the metal ; verdigris may also be in- 
troduced into food from the cooking of acid vegetables or fruits in copper 
vessels ; the use of copper in domestic economy ought, therefore, to be dis- 
pensed with as far as practicable. The best antidote against copper poison- 
ing is raw white of eggs, the albumen of which, by forming an insoluble 
compound with the metal, renders it inert. Milk, or sugar mixed with iron 
filings are also efficacious. 

615. Alloys of Copper . — The alloys of copper are extensively used 
in the arts. Brass is an alloy of copper and zinc ; the usual proportions 
being 66 parts of copper and 34 zinc. By varying the proportions, however, 
the varieties of brass known as "red metal," "pinchbeck," " Muntz," or 
sheathing metal, etc., may be obtained. Gun-metal, used in the fabrication 
of brass ordnance, is an alloy of 90 parts of copper and 10 of tin. Bell-metal 
and speculum-metal contain a larger proportion of tin. Bronze for statuary 
consist of 91 parts copper, 2 of tin, 6 of zinc, and 1 of lead. The brass of 
the ancients was an alloy of copper and tin. 



Qttestions What is said of nitrate of copper ? What is verdigris? Hot is it pre- 
pared ? What are the characteristics of the salts of copper ? Why is the use of copper 
vessels in culinary operations unadvisahle ? What is the hest antidote against copper 
poisoning ? What is brass ? What is gun-metal — bell -metal — bronze ? 



380 



INORGANIC CHEMISTRY 



616. Bismuth is a reddish-white, hard, brittle metal, 
which is generally found, native in small quantities. 

It crystallizes from fusion in cubic crystals of great brilliancy. Its principal 
employment is in the preparation of alloys, a slight admixture of it increasing 
the fusibility of several metals to a remarkable extent. Oxyd of bismuth is 
used to somp extent in medicine, and also as a cosmetic (pearl powder). 



SECTION VII. 

URANIUM, VANADIUM, TUNGSTEN, COLUMBIUM, TITANIUM, MOLYBDENUM, 
NIOBIUM, PELOPIUM, ILMENIUM, ETC. 

617. All these metals are very sparingly distributed over the surface of the 
earth, and some of them are so rare, that they have been seen by only a few 
chemists. Uranium and titanium are used to some extent for the coloration 
of porcelain and enamels ; and molybdenum, in combination, as molybdate of 
ammonia, constitutes the most delicate known test of the presence of phos- 
phoric acid in solution. 

SECTION VIII. 

ANTIMONY AND ARSENIC. 

618. Antimony.— Equivalent, 12-9; Symbol, Sb. (Stib- 
ium). — Antimony is a blueish-white metal, with a highly- 
crystalline texture, so brittle that it may be easily reduced 
in a mortar to a fine powder.* 

"When exposed to air and moisture, at ordinary temperatures, it under- 
goes no change; but if heated, it burns brilliantly, emitting copious white 
fames, which consist chiefly of a teroxyd of antimony. A very interesting 
experiment consists in fusing a little of the metal on charcoal before the blow- 
pipe, and projecting the melted globule upon the floor or an inclined board ; 
the moment it strikes the hard surface, it bursts into a multitude of little 
spheroids, which radiate in aU directions, leaving a trail of white smoke (oxyd) 
behind them. Antimony is not used by itself in the arts, but it enters into 
the composition of several important alloys, as type metal, Britannia metal^ 
etc. Pinery -powdered antimony, sprinkled into a jar of chlorine gas, ignites, 
and occasions a miniature shower of fire. 



■* Antimony was first made known by Basil Valentine, an alchemist and monk, of Er- 
furth, Germany. The etymology of its name is said to be due to the following circum- 
stance : its discoverer having observed that its effects, when administered to hogs, were 
beneficial, tried it upon his fellow-monks. The result of the experiment, however, was 
that the monks sickened and died — hence the name antimoine, anti-monk, antimony. 



Questions. — What is said of bismuth ? What are its uses ? What is said of uranium, 
titanium, and molybdenum ? What of antimony? What are the properties of antimony! 
What its industrial uses ? 



ANTIMONY . — A RSENIC. 381 

619. Antimony forms three oxyds, the most important of which are, the 
teroxyd of antimony, Sb0 3 , and antimonic acid, Sb0 5 . 

620. The compounds of antimony are remarkable for their medicinal ef- 
fects, and are classed in pharmacy among the important remedial agents. 
When taken, however, in inordinate doses, they act as poisons. Tartar 
emetic is a double salt of tartrate of potash and tartrate of antimony. It is 
formed by boiling oxyd of antimony with cream of tartar, which last is a salt 
of potassa and tartaric acid, containing free acid; this free acid combines 
with the oxyd of antimony, and thus forms a double salt. Tartar emetic, dis- 
solved in sherry wine, in the proportion of two grains of the former to a fluid 
ounce of the latter, forms the well-known "wine of antimony." 

Sulphuretted hydrogen, added to solutions of antimony (as a solution of tar- 
tar emetic in water), precipitates the metal in the form of a peculiar and highly 
characteristic, orange-colored sulphuret. 

621. Arsenic. — Equivalent, 75; Symbol, As. — Arsenic 
is sometimes found native, but generally occurs in the 
form of an alloy with some other metal, especially with 
iron, cobalt, nickel, copper, or tin. 

The greater part of the arsenic of commerce is obtained in Silesia, in Ger- 
many, by roasting, in furnaces, a double sulphuret of iron and arsenic, — called 
mispickel, or the arsenides of nickel and cobalt. The arsenic, volatilized by 
heat in the form of an oxyd — arsenious acid — is condensed and collected in 
the form of a white powder in large chambers, into which the flues from the 
furnace open.* 

Metallic arsenic may be obtained by heating arsenious acid with powdered 
charcoal in a tightly-closed crucible. It is a dark, steel-gray colored metal, 
extremely brittle, and may be easily reduced to powder. It is sold by drug- 
gists under the very objectionable names of fly-powder, fly-poison, cobalt, etc. 
"When heated, it volatilizes without fusion ; and if air be present, it oxydizes 
to arsenious acid. Its vapor has a remarkable odor of garlic, which is so pe- 
culiar and noticeable, that it is regarded as one of the characteristic tests of 
the presence of this element ; this odor is easily recognized by heating a frag- 
ment of arsenic, or arsenious acid on charcoal before the blow-pipe. 

622. The oxyds of arsenic are two : — Arsenious acid, As0 3 , and arsenic 
acid, AsC>5. 



* The opening of these chambers, and the removal of arsenic, is a task of great danger, 
and is performed about once in six weeks. The workmen engaged in the operation, aa 
protection against the poison, are completely encased in leather, with glazed apertures for 
the eyes. They also wear, in addition, damp cloths over their mouths and nostrils, in 
order to prevent the inhalation of minutely-divided particles. 



Questions. — What are the chief oxyds of antimony? What is tartar-emetic? What 
is wine of antimony ? What is a characteristic test of antimony in solution ? In what 
form does arsenic occur naturally ? How is the arsenic of commerce prepared ? What is 
said of metallic arsenic ? What of its oxyds ? 



382 INORGANIC CHEMISTRY. 

Arsenious Acid, As 2 . — White Arsenic, BaVs-bane. — This oxyd is 
the substance to which the name arsenic is popularly applied, and is the well- 
known poison. It occurs in commerce as a white powder, but when freshly 
sublimed it assumes the appearance of a semi-transparent solid, which gradu- 
ally becomes opaque and white, like porcelain. It is soluble in about 11 parts 
of boiling water, but to a very much less extent in cold water. Its solution 
is colorless, and almost tasteless, which circumstances greatly facilitate its em- 
ployment for criminal purposes. It dissolves freely in hot hydrochloric acid, 
and in solutions of the alkalies. 

Arsenious acid combines with bases to form arsenites : arsenite of potash is 
used in medicine under the name of Fowler's solution ; and arsenite of copper 
constitutes the delicate and beautiful green pigment known in commerce as 
Sclieetts green. Its poisonous properties have also been taken advantage of 
for the destruction of vermin. To destroy rats and mice, the poison should 
be mixed with flour or lard, but not in too large a quantity, or these animals 
will not touch it.* Arsenious acid, when placed in contact with organic sub- 
stances, prevents their decay, and may be hence used with advantage for the 
preservation of stuffed and dried objects of natural history.f 

623. Arsenic Acid, A s O5, is formed by treating arsenious acid with 
nitric acid, and evaporating the solution to dryness. It unites with metallic 
oxyds to form arseniates: the arseniate of potash being used to a very great 
extent in calico printing, not so much to produce colors as to prevent their 
adherence to certain portions of the fabric. 

Arsenic combines with hydrogen to form a volatile and highly poisonous 
gas — arseniuretted hydrogen. There are also several compounds of arsenic 
and sulphur, which are used as pigments and in pyrotechny: realgar, AsS3, 
is a beautiful red pigment, and is a principal constituent of the so-called white 
Indian fire, often used as a signal-light ; orpiment, AsSs, is a golden yellow 
pigment ; — both of these substances are found native. 

624. Arsenic forms alloys with most of the metals, which are generally brit- 
tle and easily fusible. Its presence in iron is highly injurious. 



* If the poison is put in stables, the receptacles of meal and fodder should be carefully 
covered over, that the poisoned rats may not vomit the poison into them. 

t It is best used for this purpose in the form of an arsenical soap, which may be pre- 
pared by mixing 100 parts of -white soap, 100 of arsenious acid, 36 carbonate of potash, 15 
camphor, and 12 quicklime. The soap is to ba scraped and melted with a little water at 
a gentle heat; then add the potassa and the lime, and mix them well together — the arsen- 
ious acid is afterward added gradually, and well incorporated. The camphor is reduced 
to powder by rubbing it in a mortar, with the addition of a few drops of strong alcohol, 
and when the soap is cold this is well mixed in. A portion of the soap dissolved in water 
ii applied to the preparations by means of a camel's hair pencil. It constantly exhales 
the odor of arseniuretted hydrogen, and effectually destroys insects and their eggs. — 
Dumas. 

Qtjestions. — What is said of the arsenic of the shops ? What are the properties of ar- 
senious acid? What are its salts termed"? What is Fowler's solution? What is 
Scheele' green ? What are the uses of arsenic ? What is arsenic acid ? What are its 
salts called ? What are its uses ? What is said of the other compounds of arsenic ? 



ARSENIC. 383 

625. Characteristics and Tests for Arsenic — The com- 
pounds of this metal are all highly poisonous, either when taken into the sto- 
mach, when applied to wounds, or when inhaled as vapor. The most effectual 
antidote?, in cases of ordinary poisoning by it, are, first, a powerful emetic, and 
then the free administration of the hydrated oxyd of iron suspended in water 
(§ 567); if this is not at hand, calcined magnesia may be used. In the ab- 
sence of either of these substances, the white of eggs, milk, sugar, and soap- 
suds are beneficial, (this latter observation applying also to almost all other 
cases of poisoning). Prompt action is, however, necessary, as arsenic is 
almost always fatal when time is allowed for its absorption into the system 
in sufficient quantity. 

The frequent employment of arsenic as an agent in poisoning, has induced 
chemists to study its nature and compounds so carefully, that its detection 
when present in the body, in the materials which have passed from the body, 
in food or in liquids, is a matter of certainty. Even though the quantity be 
too minute to be weighed, its existence in a substance may be absolutely de- 
monstrated and made visible to the eye. Lapse of time can not wholly de- 
stroy this chemical evidence ; — the body with which the arsenic has become 
incorporated may decay, but the poison remains unchanged, and may be 
recognized even after the lapse of years.* 

626. An investigation for the detection of arsenic, in cases where a criminal 
prosecution involving reputation, and perhaps life, depends upon the issue, 
should be intrusted only to a professional chemist, but a description of the 
tests employed, and of the methods by which evidence can be accumulated, 
are matters of general interest. 

An exceedingly delicate test known as "Marsh's test," depends upon the 
property which arsenic possesses of forming a gas with hydrogen, and de- 
positing itself, in the metallic state, upon the surface of a cold plate held 
over the flame of the burning gas. The experiment is made by generating 
hydrogen in the usual manner from zinc, water, and sulphuric acid, in a glass 
flask, and allowing it to escape through a perforated cork and tube of glass 
drawn down to a fine point. (See Fig. 200.) The hydrogen evolved should 
first be tested by burning it against a porcelain plate to prove that it is free 
from arsenic, and then the suspected liquor is to be introduced into the ap- 
paratus. (For the purpose of experiment a few drops of a solution of arsenious 
acid in water, or hydrochloric acid, may be used). If arsenic is present, the 
flame of hydrogen, when brought in contact with the surface of a cool white 



* In cases of arsenical poisoning, putrefaction of the body after death is retarded in a 
remarkable degree ; and in many cases where the body has been disinterred several months 
after death, it has been found sufficiently preserved from decay to allow many of the 
principal internal organs to be distinguished. In one instance, in France, conviction of 
poisoning by arsenic was obtained on evidence procured by the celebrated chemist Or- 
filla, from the remains of a person who had been dead for a lengthy period of years. 

Questions. — What is said of the poisonous effects of arsenic ? What of its antidotes ? 
What is 6aid of its detection in the body, or in other substances? What is Marsh' a 
test? 



384 



INORGANIC CHEMISTRY. 



plate, or saucer, will deposit a smooth black or 
brown spot (a little metallic mirror). One other 
metal — antimony — will give the same reaction, 
but a drop of an aqueous solution of chloride 
of lime instantly dissolves the arsenic spot, but 
leaves the antimony unaltered. If the arseni- 
uretted hydrogen gas be conducted through a 
glass tube heated at one point over a spirit- 
lamp, metallic arsenic will be deposited in the 
colder part of it, forming a beautiful incrus- 
tation. 

Sulphuretted hydrogen precipitates arsenic 

from its solutions in the form of a sulphuret of 

arsenic, of a rich lemon color. This is a very 

accurate test, and so delicate that the yellow 

tint is apparent when only a ten-thousandth part of arsenious acid is present, 

and a precipitate when the proportion is as 1 part of arsenious acid to 80,000 

of water. 

Reduction of the metal from its oxyds or sulphurets is a test much relied 
on in judicial investigation. This may be effected by introducing a little ar- 
senious acid, or the sulphuret obtained in the last experiment, mixed with 
finely-powdered charcoal and carbonate of soda, into a glass tube of the 
diameter of a common quill, care being taken not to soil the sides of the tube. 




Fig. 201. 




The mixture is then gently heated by the 

flame of a spirit-lamp, when the metallic 

arsenic sublimes, and is condensed as a 

black, lustrous mirror, c, in the upper 

and cool part of the tube. (See Fig. 201.) 

A slip of bright metallic copper, placed 

in a hot solution of arsenious, or arsenic 

acid, acidulated by hydrochloric acid, is 

soon coated by a gray film of metallic 

arsenic. This is known as Reinsch's 

test, and is affirmed to show the presence 

of a 250,000th part of arsenic in solution. It is a test readily applicable even 

when the solution is contaminated by the presence of so much organic matter 

as to impair the accuracy of other reactions. 

A dose of from 2 to 3 grains of arsenic is generally regarded as fatal, 
though larger doses are sometimes rejected from the stomach by vomiting. 
A dose of from l-15th to l-30th of a grain is said to warm and exhilarate 
the system, and increase its vigor, and the peasants of Hungary are reported 
to be in the habit of using it for this purpose. 

Questions. — What other metal gives the same reaction? How may antimony he dis- 
tinguished from arsenic in this instance ? What is the test by sulphuretted hydrogen ? 
What is the test by reduction? What is Reinsch's test? What amount of arsenic is 
fatal ? 



MERCURY. 385 

627. Arsenic and antimony are the only metals which are capable of com- 
bining with hydrogen. In this and several other respects, they comport them- 
selves like metalloids, and by some chemical authorities arsenic is regarded 
as a non-metallic element. 



CHAPTER XIV. 

THE NOBLE METALS. 



-t 



The metals included in this class are nine in number, 
viz., Mercury, Silver, Gold, Platinum, Palladium, Bho- 
dium, Kuthenium, Osmium, and Iridium. 

The principal characteristic of these metals is their slight affinity for oxy- 
gen, by reason of which their oxyds are easily decomposed by the action of 
heat alone, the metal remaining in an uncombined state. The temperature 
required to effect this decomposition is less than red heat, with the single 
exception of the oxyd of osmium. Mercury and silver are generally found 
in nature as sulphides ; the others usually occur native, and are often asso- 
ciated with each other. 

SECTION I. 

mercury {Hydrargyrum, liquid silver). 

Equivalent, 100. Symbol, H. Specific gravity, 13*59. 

628. Natural History and Distribution . — Mercury is some- 
times found native, as fluid quicksilver, but most generally occurs as a sulph- 
ide, forming a brilliant red mineral termed cinnabar. Its most productive 
mines are those of Almaden in Spain, Idria ih'"3!us!rTa, and New Almaden 
in Upper California. Considerable quantities are also obtained from locali- 
ties in Mexico, Peru, China, and Japan. It is reduced from its ores by a pro- 
cess of distillation. 

629. Properties . — Mercury is a brilliant, silver- white metal, possess- 
ing great density, and also the remarkable property of remaining fluid at 
common temperatures. It solidifies (freezes) at — 39° K, in which state it 
is soft and malleable. "When heated to 662° F. it boils, and yields an in- 
visible vapor. The metal also, at all temperatures above 40° P., undergoes a 
slight spontaneous evaporation — a fact easily proved by the action exerted 

Questions. — What are distinguishing characteristics of antimony and arsenic ? What 
are the noble metals ? What are their characteristics? Under -what circumstances does 
mercury occur naturally ? Where are its principal mines ? What are its properties ? At 
what temperature does it solidify ? When boil ? What is said of its volatility ? 

17 



386 INORGANIC CHEMISTRY. 

upon a sensitive daguerreotype plate suspended a few inches above a vessel 
containing mercury. 

Mercury, when pure, is not tarnished by exposure to air and moisture at 
ordinary temperatures, but when heated to near its boiling point it slowly 
absorbs oxygen, and becomes converted into a crystalline, dark-red powder, 
the red oxyd of mercury. This oxyd, when subjected to a dull red heat, 
evolves oxygen, and is decomposed into its constituents. It was by means 
of this substance that Priestley first discovered the existence of oxygen, and 
Lavoisier determined the composition of atmospheric air. 

630. The most ready solvent of mercury is nitric acid, which dissolves ic 
with great rapidity. Hydrochloric acid has no action upon it, and the same 
is true also of dilute sulphuric acid. 

631. "When pure mercury is agitated with ether, or oil of turpentine, or 
rubbed with sulphur, sugar, chalk, lard, etc., it is reduced to so fine a state 
of division that it loses its metallic appearance entirely, and becomes thor- 
oughly incorporated with the foreign body. In its ordinary state, mercury 
is inactive as a medicine, but in this state of mechanical division it is readily 
absorbed by the system, and becomes efficacious. The well-known blue-pill 
is mercury rubbed into a gummy compound, called " confection of roses;" and 
mercurial ointment is mercury incorporated with lard. 

632. Mercury combines with oxygen in two proportions, forming a gray, 
or suboxyd, HysO, and the protoxyd, or red oxyd, HyO. This last oxyd is 
a red powder, and was called by the old chemists red precipitate. 

633. Mercury forms two compounds with chlorine, which correspond in 
constitution to the two oxyds, and are of great importance in medicine and 
the arts ; they are the subchloride and the chloride. 

634. Subchloride of Mercury, H y 2 C 1 , is the well-known medi- 
cine, calomel. It may be obtained by precipitating a solution of sub-nitrate 
of mercury with common salt. "When pure, it is a heavy, white, insoluble, 
and tasteless powder. 

635. Chloride of Mercury, II y C 1 , is known in commerce under 
the name of corrosive sublimate. Its formation may be shown experimentally 
by heating a globule of mercury in a deflagrating spoon, and plunging it 
into a jar of chlorine ; the metal takes fire and produces the chloride. Prac- 
tically, it is prepared by subliming a mixture of common salt and sulphate 
of protoxyd of mercury. 

Corrosive sublimate is a dense, white crystalline substance, soluble in 16 
parts of cold, and 3 of boiling water — its solution possessing a disgusting 
and burning metallic taste. It is one of the most deadly poisons known in 
chemistry. With albumen it unites to form compounds which are nearly 
insoluble ; hence substances which contain albumen, such as white of eggs, 
milk, etc., are the most effectual antidotes in cases of poisoning by it. Timber, 

Questions. — What of its power to resist oxydation ? What is its most ready solv- 
ent ? What of its susceptibility to mechanical division ? What is blue-pill ? What mer- 
curial ointment ? What are its oxyds ? What is said of its chlorides ? What is calo- 
mel ? What is corrosive sublimate? What are its T/->T) er ti e s ? What are antidotes to it? 



MERCURY. 387 

and animal and vegetable substances in general, are effectually protected 
against decay and the action of insects, by steeping in a solution of corro- 
sive sublimate. This process is known in the arts as kyanizing, from its in- 
ventor, Mr. Kyan, who first applied it with great success for the protection 
of ship-timber against the effects of " dry rot." The preservative action ap- 
pears to be due to the circumstance that the corrosive sublimate unites 
with the organic substances to produce insoluble and poisonous com- 
pounds. A solution of corrosive sublimate in alcohol is much used as a 
preservative wash for plants in herbariums, and for other- objects of natural 
history. 

636. Oxyd of mercury forms several salts with nitric acid, the principal 
of which are the subnitrate, Hy20,NO-5, and the nitrate, HyO,N0 5 . The last- 
named salt is used in the arts as a wash for rabbit and hare skins, as it im- 
parts to these furs a property of felting which does not naturally belong to 
them. 

63*7. Sulphide of Mercury, HyS .—This compound is tho most 
abundant of the ores of mercury, and as a mineral product is termed cinna- 
har; but when prepared artificially, it constitutes the beautiful red pigment 
known as vermilion. Vermilion is prepared by subliming 1 part of flowers 
of sulphur with 6 of mercury. The product is a blackish-red crystalline 
mass, which by friction and pulverization assumes a magnificent scarlet color. 

638. Uses . — Mercury is used extensively in the arts in the construction 
of philosophical instruments (barometers, thermometers, etc.), in the extrac- 
tion of gold and silver from their ores, in gilding, and in medicine. 

639. Alloys of Mercury with other metals are termed amalgams. 
An amalgam of 4 parts of tin to 1 of mercury constitutes the material em- 
ployed for the silvering of mirrors. A strip of copper becomes amalgamated 
if rubbed with a solution containing mercury. If we make a stroke across 
a brass plate with a stick or brush dipped in a solution of mercury, and af- 
terward bend the plate at this place, it will break as though it had been 
cut; the explanation of this is, that the mercury of the solution at once 
penetrates and combines with the brass, and renders it extremely brittle. 
Mercury, when brought in contact with bars of lead, tin, and zinc, readily 
permeates them by a species of capillary attraction; and by employing a bar 
of lead in the form of a syphon, we may gradually raise and draw off mer- 
cury from its containing vessel. 

Tin, lead, silver, gold, and several other metals, aro dissolved by mercury 
to a considerable extent, without much loss of fluidity. It has, on the con- 
trary, but little attraction for iron, and on this account it is generally pre- 
served in iron bottles. 

The presence of mercury, when in solution, may be detected by placing a 

Questions. — "What is kyanizing ? How does corrosive sublimate act as a preserva- 
tive agent ? What is said of the nitrates of mercury ? "What is vermilion ? How is ifc 
prepared ? What are the principal uses of mercury ? What are alloys of mercury termed ? 
What forms the lustrous coating of mirrors? How does mercury comport itself in con- 
tact with the other metals ? How may the presence of mercury in solution be detected ? 



38'8 INORGANIC CHEMISTRY. 

drop of tho suspected liquid on a piece of polished gold, as a half-eagle, and 
touching the metal, through the liquid, with a scrap of zinc, or with the point 
of a penknife. The part touched will instantly appear white, owing to the 
deposition of mercury by voltaic action. 



SECTION II. 

SILVER. 
Equivalent, 108. Symbol, Ag. (Argentum). Specific gravity, 10-5. 

640. Natural History and Distribution. — Silver is fre- 
quently met with in the native state, hut most generally it is found in com- 
bination with sulphur, mixed with sulphides of lead, antimony, copper, and 
iron. The mines of Mexico and Peru are the most productive sources of sil- 
ver ; but it occurs in quantities sufficient to pay for working, in Norway, Sax- 
ony, Spain, and the Hartz mountains. 

641. Amalgamation . — Silver is obtained from ores free from lead, as 
those of South America and Mexico, by a process termed Amalgamation, 
which is founded upon the ready solubility of silver and other metals in met- 
allic mercury. The ore is first crushed to a fine powder, mixed with common 
salt, and roasted at a low red-heat in a furnace. By this treatment the silver 
obtains chlorine from the salt, and is changed from a sulphide into a chloride. 
The resulting products of the furnace, consisting of chloride of silver, oxyds 
of copper, iron, and earthy matters, are then placed, with water and a portion 
of scrap iron, in barrels which revolve upon their axes, and the whole agitated 
together for some time, during which the iron reduces the chloride of silver to 
a state cf metal, and forms chloride of iron ; a certain portion of mercury is then 
added, and the agitation continued. The mercury dissolves out the silver, the 
copper, and the gold, if there be any, and combines with them to form an 
amalgam; which, by reason of its great weight and fluidity, is easily separ- 
ated from the other materials by washing and subsidence. This amalgam is 
then pressed in woolen bags, to squeeze out the uncombinod mercury, and the 
solid portion heated in a kind of retort, when the last trace of mercury vol- 
atilizes, and leaves the silver alloyed with copper or gold behind. In this 
state it is exported in ingots.* 



* This process, as conducted in Mexico and South America by the rude miners, is ex- 
ceedingly imperfect, and is attended with an enormous loss of quicksilver, by volatiliza- 
tion and the formation of calomel, Hy2Cl; so much so, that it has been calculated that 
upwards of six million cwt. of mercury had been wasted in the American mines up to the 
close of the last century. It must be, therefore, apparent, that the great employment of 
mercury is in the mining of silver; and previous to the discovery, a few years since, of 
the '•ich cinnabar mines of California, the price of mercury (owing to a diminished sup- 
ply from the mines in Spain and Austria) had risen so high, that many of the richest sil- 
ver-mines of Mexico and Peru were of necessity abandoned. 

Questions. — What is said of the natural condition of silver ? Where are its principal 
minej? How is silver obtained from its ores by amalgamation? 




SILVER. 389 

642. Liquation . — Silver containing a large percentage of copper is sep- 
arated from this metal by what is called the process of Liquation: this con- 
sists in melting the two metals with a large proportion of lead, and cooling 
the mixture suddenly in the form of cakes ; these are then exposed, on an in- 
clined hearth, to a temperature sufficient to melt the lead, but not the copper, 
when the former metal runs off, and carries all the silver with it, leaving the 
solid copper behind. 

643. Cupellation — Silver is parted from lead by a process termed 
Cupellation. It consists in exposing the mass, in the first instance, to a red- 
heat, upon the hearth of a shallow furnace, while a current of air is caused to 
play upon its surface ; the lead rapidly oxydizes, and is converted into lith- 
arge, which, in turn, melts and runs off, leaving the metallic silver unoxyd- 
ized, and in a nearly pure state (refined silver). The hearth upon which this 
operation is conducted, is called a cupel, and is formed by molding pulverized 
bone-ashes into the shape of an oval, shallow basin. 
In order to render the silver thus obtained still purer 
(fine silver), it is again fused under the same circum- 
stances in small cupels (Fig. 202) ; by which, the last 
remaining traces of lead, and all other metallic impur- : 
ities, except gold, are converted into oxyds, and ab- 
sorbed by the porous bone-ash. 

^ss 644. Properties . — Silver has the clearest white color of all the metals. 
It is malleable and ductile in a high degree, and in hardness is intermediate 
between gold and copper. It melts at a bright red- heat, 18 7 3° P., expand- 
ing forcibly at the moment of solidification ; and is not oxydized by exposure, 
at any temperature, to either a dry or moist atmosphere. Pure silver, how- 
ever, possesses the remarkable property of mechanically absorbing oxygen, 
when melted, to the extent of many times its volume. This oxygen is again 
disengaged at the moment of solidification, and gives rise to the peculiar ar- 
borescent appearance often noticed on the surface of masses of silver. Silver 
has a powerful affinity for sulphur ; and when exposed to air containing very 
minute quantities of sulphurous acid, or sulphuretted hydrogen, it soon be- 
comes superficially blackened or tarnished, from the formation of a thin film 
of sulphide upon its surface* 

The best solvent of silver is nitric acid, which acts upon the metal with 
great rapidity ; if the silver contains any gold, it will be left undissolved as a 
dark powder. Solution of silver coin in nitric acid appears of a bluish-green 
color, from the copper it contains. Hydrochloric acid scarcely acts upon silver, 
and sulphuric acid only when hot 

* The air of large towns or cities, and the air of rooms in which mineral coal or coal- 
gas is burnt, always contains sufficient of the gaseous compounds of sulphur to gradually 
tarnish silver. 

Questions. — How is silver obtained by amalgamation freed from copper? What is this 
process termed ? How is silver freed from lead ? What is a cupel ? What are the propr 
erties of silver ? What are the relations of fused silver and oxygen ? What of silver and 
sulphur ? What are the solvents of silver ? 



390 INORGANIC CHEMISTRY. 

645. Oxyds of Silver . — Silver forms three oxyds — the suboxyd, 
Ag20 ; the protoxyd, AgO ; and a peroxyd, AgO* 

646. Protoxyd of Silver is the only oxyd which forms permanent 
salts, and may be procured by adding potash or soda to a solution of the 
nitrate, or any soluble salt of silver. It is a dark-brown or black powder, 
soluble in ammonia, and to a slight extent in pure water. Its solution in 
cyanide of potassium constitutes the silver solution used in electro-plating. 
Oxyd of silver is decomposed at a temperature below red heat, and to some 
extent also by the action of solar light. 

647. Nitrate of Silver, A g , N 0s. — This is the most important 
of the salts of silver, and may be obtained in the form of colorless, transparent, 
tabular crystals, by dissolving silver in nitric acid, and evaporating the solu- 
tion to dryness. The crystals thus obtained are readily soluble in water, and 
when fused and cast into slender sticks, they constitute the lunar caustic of 
the surgeon.* 

Nitrate of silver, when perfectly pure, undergoes no change by the action 
of light, but when exposed to light in contact with organic matter, it blackens 
rapidly. Stains thus produced by it can not be removed by washing with 
soap and water ; hence nitrate of silver constitutes an essential ingredient in 
the composition of hair-dyes, and the indelible inks used for marking linen. 
Ivory, marble, and other bodies, may be stained a permanent black by soak- 
ing in a solution of this salt, and then exposing to the direct action of the 
sun's rays. The black coloring matter is by some supposed to be silver in 
a state of fine division, and by others to be a suboxyd of silver. It may be 
removed from the hands, or from linen, by the employment of a strong so- 
lution of iodide of potassium, or more easily by cyanide of potassium. Ni- 
trate of silver is sometimes given as a medicine ; if the administration of it 
is long continued, a portion of the silver in combination tends to find its way 
out of the system at the surface of the body ; but becoming decomposed by 
the action of light before it reaches the outer surface of the skin, it imparts 
to all those portions of the body exposed to light a singular blue or lead-gray 
color. This color, from the circumstance that it is formed below the outer 
skin (or cuticle), is perfectly indelible, f 



* The corrosive power of lunar caustic is not the result of any specific action of the 
nitrate of silver but of the nitric acid, which is liberated by the decomposition of the 
Bait when in contact with organic matter. 

t A most singular case of this discoloration was to be seen a few years since in the city 
of New York, in the person of an itinerant book-agent, who was familiarly called the 
" blue man." The color of this person, owing to an injudicious use of nitrate of silver 
as a remedy for epilepsy, was generally of a dark, dull blue, varying to brown with shades 
of green. 

Questions What oxyds of silver are there ? What is the principal oxyd ? How is 

it prepared ? What are its properties ? How is nitrate of silver prepared ? What is lu- 
nar caustic ? What action has light upon this salt ? Into what articles does it enter as an 
essential ingredient? How may nitrate of silver stains be removed? What sometimes 
happens wnen nitrate ot silver is taken into the system ? 



SILVEK. 391 

When a stick of phosphorus is introduced into a solution of nitrate of 
silver, it soon becomes incrusted with arborescent crystals of the metal. The, 
introduction of mercury into a solution of nitrate of silver also precipitates 
the metal in beautiful tree-like forms which are called arbor Diance. Metallic 
copper at once throws down metallic silver from solutions of the nitrate, 
and forms nitrate of copper. 

648. Chloride of Silver, AgCl ■ — This compound appears as a 
white, curdy precipitate when hydrochloric acid, or the solution of any chlo- 
ride (as common salt) is added to a solution of silver. Its formation, under 
these circumstances, constitutes a most delicate test for the presence of silver 
in solution, as the chloride of silver is so entirely insoluble in water, that a 
millionth part of it will occasion a cloudiness of the solution. It is, however, 
readily soluble in ammonia, and when exposed to the light, quickly assumes 
a violet color. Chloride of silver, kept in solution by the alkaline chlorides, 
probably exists in minute quantities in all sea-water. MM. Malagutti and 
Durocher, eminent French chemists, have estimated, on the basis of recent 
experiments, that each cubic mile of sea-water contains lOf lbs. of silver in 
the form of chloride. 

649. Uses . — Pure silver, by reason of its softness, is not used to any ex- 
tent in the arts ; but for coin, plate, etc., it is always alloyed with a propor- 
tion of copper, which greatly increases its hardness without materially dimin- 
ishing its whiteness, and thus renders it less liable to be worn by use. 
The amount of copper that may be alloyed with silver for the manufacture of 
coin is always regulated by government. In Great Britain, standard silver 
is composed of 11 parts of silver and 1 of copper; in the United States, all 
gold and silver coin consists of nine tenths pure metal and one tenth alloy. 
In England and France, the government also regulates the purity of silver 
used for the manufacture of plate ; in the United States the manufacturer 
alloys his silver at discretion. 

Silver is frequently employed to give a coating to less expensive metals. 

Plating on copper is effected by laying a strip of silver upon a bar of cop- 
per, and uniting the two metals (without solder) by hammering and rolling 
at a temperature just below the fusing point of silver. The compound ingot is 
then rolled to the required degree of tenuity. Silvering, or covering the sur- 
face of brass or copper with a thin coating of silver, may be effected by first 
thoroughly cleaning the surface to be silvered by momentary immersion in 
nitric acid, and then rubbing, with a mixture of cream of tartar (100 parts), 
chloride of silver (10 parts), and corrosive sublimate (1 part) ; the surface is 
afterwards polished. It is in this way that thermometer scales are silvered. 
A peculiar blanched or " dead" appearance may be given to articles manufac- 
tured from an alloy of silver and copper, by boiling them in a solution of bi- 

Qukstions. — What is said of chloride of silver ? What is a test of the presence of sil- 
ver in solution? Does silver exist in sea-water? In what state is silver used in the arts? 
What is standard silver in Great Britain and the United States ? How is plating effected ? 
How may articles be silvered ? What is dead silver ? 



392 



INORGANIC CHEMISTRY. 



sulphate of potash ; the acid of which dissolves out the copper from the sur- 
face, and leaves the particles of silver isolated. 

650. Silvering of Glass .-—Certain organic substances, such as oil 
of cassia, oil of cloves, or solution of grape-sugar, possess the property, when 
added to certain salts of silver in solution, of precipitating the silver in the 
state of bright, lustrous metal. This principle has been recently applied to 
the silvering of glass ; and many articles of great beauty, such as mirrors, 
glass-globes, vases, door-knobs, etc., are now coated in this manner.* 



SECTION III. 



x. 



Fig. 203. 



Fig. 204. 



Equivalent, 98-7. Symbol, Au. (Aurum). Specific gravity, 19.2. 

651. Natural History and Distribution. — Gold is 
found native or in the metallic state ; generally in the form of thin scales or 
grains, sometimes as large, nodular masses, f and some- 
times in crystals; the last being al- 
ways modifications of the cube, or 
octohedron. (See Figs. 203 and 204.) 
Native gold is always alloyed with 
silver, and is often associated with small 
quantities of osmium, iridium, copper, 
antimony, sulphuret of iron, and rarely 
with tellurium. No regular veins of 
gold are met with (what are called veins of gold being 
merely veins of quartz containing disseminated metallic particles). It com- 
monly occurs in the most ancient rocks, or in the alluvial deposits of rivers. 
As gold is found naturally in a metallic state, the operations for obtaining it 
are almost purely mechanical, as washing, etc. When the gold is very finely 
divided and mixed with earthy matters or other metals, it is separated by a 
process of amalgamation similar to that already described for obtaining silver. 
(See § 641.) 





* A composition for silvering glass may be prepared as follows : — Mix 30 grains aqua 
ammonia, GO nitrate of silver (crystals), 90 spirits of -wine, and 90 of water. When the 
nitrate of silver is completely dissolved, filter the liquid and add 15 grains of grape sugar 
dissolved in a mixture of 1£ ounces of water and lh ounces spirits of wine. For silvering 
a glass, it is sufficient to leave this solution in contact with the glass for a space of two or 
three days ; but by heating the mixture, the effect may be produced rapidly. 

t A mass of gold once found in North Carolina weighed 28 pounds ; a mass found in 
the Ural Mountains, and now in the Imperial Cabinet of St. Petersburgh, has a weight of 
nearly 80 pounds. Masses, however, of larger size, mingled with quartz, have been since 
found in both California and Australia. 



Questions. — How may glass be silvered ? What is said of the natural occurrence of 
gold ? What metals usually occur associated with it ? How is gold obtained from the 
earth? 



GOLD. 393 

p 

652. Properties . — Gold possesses a characteristic yellow color and a 
high metallic luster. It is the most malleable of all the metals, and may be 
beaten into leaves which do not exceed 1-200, 000th of an inch in thickness. 
It also possesses a high degree of tenacity. When pure, gold is nearly as 
soft as lead. It fuses at a temperature of 2016° F., and can not be advan- 
tageously employed for castings, as it shrinks greatly in solidifying. Gold 
does not combine directly with oxygen at any temperature ; none of the sim- 
ple acids, with the exception of the selenic, have any effect upon it ; neither 
has sulphur or sulphuretted hydrogen. Chlorine and bromine attack it easily, 
and it is dissolved by any solution that liberates chlorine. The most usual 
solvent of gold is aqua regia. (See § 361.) 

653. Compounds of Gold . — There are two oxyds of gold, a prot- 
oxyd, AuO, and a peroxyd, or auric acid, AUO3. Both are unstable com- 
pounds, and are decomposed by the action of light. "With chlorine, also, 
gold unites in two proportions to form a protochloride, AuCl, and a perchlo- 
ride, AuCl 3 . The last is the most important compound of gold, and is always 
produced when gold is dissolved in nitromuriatic acid. 

By cautiously evaporating the solution of gold in aqua regia, the perchloride 
may be obtained in the form of yellow crystals, soluble in water, alcohol, and 
ether. If a solution of crystallized chloride of gold be applied to the skin, or 
any other organic substance, it imparts to it, on drying, a purple-colored stain. 
If a few drops be added to a dilute solution of protochloride of tin, a most 
beautiful purple precipitate is formed, which is known as the purple of Cos- 
sius. This compound of gold and tin is extensively used in enamel and por- 
celain painting, and also for imparting to glass a rich rose or purple color. 

Polished steel dipped into an ethereal solution of perchloride of gold, decom- 
poses it, and becomes covered with a coat of metallic gold : delicate cutting 
instruments are gilt in this way. Silk ribbons may be also gilt by moistening 
them with this solution, and exposing them to a current of hydrogen, or phos- 
phuretted hydrogen gas. 

Ammonia added to a solution of chloride of gold, produces a yellowish- 
brown precipitate, aurate of ammonia, or fulminating gold; this compound 
explodes at a moderate heat, or by friction. 

654. Industrial Uses of Gold . — Gold intended for coin and most 
other purposes, is always alloyed with a certain proportion of silver or cop- ' 
per, in order to increase its hardness and durability. Gold for coinage is 
usually alloyed with copper to the amount of about 10 per cent. 

The quantity of pure gold contained in a given mass is expressed by the 
word carat, used in reference to a certain standard number ; which number in 
the United States is 24. Thus, perfectly pure gold is said to be 24 carats 



Questions. — What are the characteristic properties of gold? What is said of its rela- 
tions to oxygen ? What of its solubility ? What are the principal compounds of gold ? 
How is perchloride of gold prepared ? What are its properties? What is the " purple 
of Cassius?" How is steel gilded? What is fulminating gold? In what condition is 
gold used in the arts ? How is the purity of gold expressed ? 

17* 



894 INORGANIC CHEMISTRY. 

fine; when, on the other hand, gold is spoken of as 18 carats fine, it is under- 
stood that the mass consists of 18 parts (three fourths) gold, and 6 parts (one 
fourth) alloy. 

The determination of the amount of pure gold or silver in a given mass of 
metal, is called assaying ; and as the value of all the various gold and silver 
coins in the world is regulated by the operation, the various processes con- 
tained in this department of chemistry have been carried to a high degree of 
perfection. 

655. Preparation of Fine Gold .—The process of obtaining fine 
gold, or of separating gold from its alloys of silver and copper, depends upon 
the solubility of silver and copper in nitric acid, and the perfect insolubility of 
gold in the same liquid. In order to effectually carry out the operation, it is 
necessary that the silver should amount to at least three times the weight of 
gold, or otherwise portions of silver will be mechanically protected from the 
action of the acid, and the separation be incomplete. If, therefore, the alloy 
be found to contain more than one fourth of its weight of gold, sufficient 
silver is added to reduce it to this proportion ; and hence this method of part- 
ing the metals is known in assaying as quartation. The gold remaining un- 
dissolved in the acid is collected and melted into ingots, while the silver is 
separated from the copper in solution by precipitation with common salt as a 
chloride, and subsequently reduced by contact with metallic zinc. The sepa- 
ration of gold from its alloys may also be effected by boiling the gold in sul- 
phuric acid, which dissolves the silver and the copper, but leaves the gold 
unchanged. 

When a solution of protosulphate of iron is added to a solution of perchloride 
of gold, metallic gold is precipitated in the form of a fine brown powder, which, 
when diffused in water and viewed by transmitted light, appears green ; the 
gold thus obtained is perfectly pure, and appears dark, by reason of its ex- 
treme subdivision. "When rubbed and pressed, it regains its characteristic color. 

656. Gold Leaf is manufactured by first forging tho gold into plates, 
and rolling them into thin ribbons by means of steel rollers. The ribbon is 
then divided into small squares, which are placed between leaves or sheets of 
gold-beaters' skin (a thin membraneous substance obtained from the intestines 
of animals), and the whole beaten with a heavy hammer. As the gold ex- 
pands, it is divided and subdivided until the required thinness of leaf is ob- 
tained. 

The commercial value of pure silver is about $16 per pound; a dollar coin 
weighs an ounce troy. The value of fine gold is about fifteen times greater 
than that of silver, an ounce being worth from sixteen to eighteen dollars. 

Bullion is the term applied to gold and silver reduced from the ore, but not 
yet manufactured ; at the mint it means all gold and silver suitable for coin- 
age. 

Questions. — What is meant by gold 18 carats fine ? What is assaying ? How is gold 
parted from its alloys ? What is understood by quartation? How may brown metallic 
gold be obtained ? How is gold leaf manufactured ? What is the comparative value of 
silver and gold ? What is bullion ? 



PLATINUM. 395 

SECTION IV. 

PLATINUM, PALLADIUM, RHODIUM, RUTHENIUM, OSMIUM, IRIDIUM. 

657. Platinum . — Equivalent, 98 - 7. ; Symbol, Pt. ; Specific gravity, 21*5. 
— Platinum (little silver) is not an abundant metal, and is always found na- 
tive, usually in the form of small flattened grains, but sometimes in nodular 
masses of considerable size. It is very rarely met with imbedded in rock, 
but is always obtained from alluvial deposits (sand, etc.) by washing - . The 
principal localities which furnish platinum are situated upon the western 
slope of the Ural mountains in Russia, in Brazil, and Borneo. It was first 
recognized as a distinct metal about the middle of the last century (1749). 

658. Properties . — Platinum is a grayish-white metal, intermediate in 
hardness between copper and iron ; it exceeds in tenacity all the metals ex- 
cept iron and copper, and is only inferior in ductility to gold and silver. It 
may also be beaten into thin laminae like gold leaf, and at a white-heat may 
be welded like iron. The most valuable property, however, of platinum, is its 
infusibility, which is so great that it resists the most intense heat of a wind 
furnace, and only yields to the heat generated by the oxyhydrogen blow-pipe, 
or the voltaic battery. It alloys readily with lead, iron, and many other 
metals ; and the compounds thus formed are much more fusible than pure 
platinum. Care, therefore, must be taken in using platinum crucibles, not to 
heat in them oxyds of fusible and easily-reduced metals, as lead, tin, bismuth, 
etc. ; since, in the event of the reduction of the oxyd, the crucible would be 
destroyed by the formation of a fusible alloy. 

Platinum does not oxydize in the air at any temperature, and none of tho 
simple acids have an effect upon it. Aqua regia dissolves it, but less readily 
than gold ; and it is also corroded by heating to redness in contact with the 
caustic alkalies, or with phosphoric acid in tho presence of carbon. 

The great infusibility of platinum, and its power of resisting chemical 
agents, give it a high value as a material for tho construction of apparatus to 
be used in the manufacture of powerful acids, and in chemical analysis. It is 
also extensively emplo} T ed by dentists for tho setting of artificial teeth,* and 
to some extent for the bushing of the touch-holes of guns. An attempt was 
made in Russia some years since to employ platinum for coinage, but it was 
found to be inconvenient, and the experiment lias now been abandoned. The 
value of crude platinum is about half that of gold ; but in its manufactured 
state it sells for from $18 to $20 per ounce. 

The process employed for working it depends upon its property of welding 



* The value of the platinum annually required for this purpose at the present time in 
this country, is estimated at $150,000. 

Questions How is platinum found in nature? What are its principal localities? 

When -was it discovered ? What are the general properties of platinum ? What is said 
of its infusibility? What of its alloys ? What of its solubility ? What are its industrial 
uses ? How is it manufactured ? 



396 INORGANIC CHEMISTRY. 

at high temperatures. The crude grains are first purified by dissolving in 
aqua regia and precipitating as chloride of platinum, which is subsequently re- 
duced to a metallic state by heat. It is then, in connection with scrap pla- 
tinum, fused into little ingots by the oxyhydrogen blow-pipe, and these are 
subsequently welded and rolled into bars or sheets. The working of it was 
formerly confined wholly to France, but within a few years past it has been 
introduced somewhat extensively as a business in this country. 

Platinum exists in two states of minute subdivision, viz., as spongy platinum, 
and platinum black. The properties and preparation of spongy platinum have 
been already described (§§ 48, 296). Platinum black is the metal in a state 
of such fine subdivision, that it has the appearance of soot. It is easily pre- 
pared by slowly heating to 212° F., with frequent agitation, a solution of 
chloride of platinum, to which an excess of carbonate of soda and a quantity 
of sugar have been added. The precipitated black powder is collected on a filter, 
washed and dried. Platinum black possesses the power, in a much higher 
degree than spongy platinum, of condensing gase3, and oxydizing alcohol and 
ether (§ 469). 

659. Platinum forms two oxyds, PtO and Pt0 2 , and two chlorides, PtCl 
and PtCl2. The last named compound, the bi-chloride of platinum, is the 
most important soluble salt of platinum, and is always formed when platinum 
is digested in aqua regia Its crystals, obtained by evaporating its acid solu- 
tion, form with water a rich orange-colored liquid, which is much valued in 
chemistry as the only reagent which precipitates potassa from its solutions. 

660. Palladium, Rhodium, Ruthenium, Osmium, and 
Iridium, — These metals are found only in exceedingly 
small quantities, and usually occur associated with pla- 
tinum, which metal they resemble generally in their prop- 
erties. 

Palladium is a white metal, more brilliant than platinum, very infusible, 
malleable, and ductile. Its hardness, whiteness, and inalterability would ren- 
der it exceedingly valuable in the arts if it coula be obtained in sufficient 
quantities. The Royal Geological Society of Great Britain award a medal of 
palladium for eminent discoveries in this department of science. Iridium is 
found alloyed with osmium, very often in California gold, forming the mineral 
iridosmine, which is the hardest of all known alloys. Iridium is a white, hard, 
brittle metal, more infusible than platinum, and one of the heaviest of the metals, 
being nearly 22 times heavier than an equal bulk of water. It has been used 
to some extent for forming the tips of gold pens. 

Qttestions.-— In -what two states of subdivision does metallic platinum exist? Give the 
properties of spongy platinum. How is platinum black prepared ? What compounds 
does platinum form ? What is its most soluble salt ? For what reaction is bi-chloride of 
platinum distinguished ? What is said of the other metals included in the group of noble 
metals ? What of palladium ? What of iridium ? 



PHOTOGRAPHY. 397 

CHAPTER XV. 

PHOTOGRAPHY. 

661. Photography (light-drawing) is the art of drawing, 
or producing pictures, or copies of objects, by the action 
of light upon certain chemical preparations. 

The whole art is based upon the circumstance, that the chemical element 
of the solar raj is capable of blackening or discoloring certain compound sub- 
stances exposed to its influence, the principal of which are various salts of 
silver.* This fact has been long known and recognized, and as far back as 
1802, Sir Humphrey Davy succeeded in obtaining images upon paper or 
white leather prepared with nitrate of silver, by exposure in a camera ob- 
scura ; — the parts of the surface subjected to a strong light being blackened, 
while those in the shadow, which were unacted upon, remained white. It was 
found, however, impossible to arrest the action thus generated, and the image 
formed soon disappeared by a continuous darkening of the whole surface. 
The subject appears to have been next taken up by M. Niepce, a French 
gentleman of Chalons, who ascertained, in 1823, that when a surface of a pe- 
culiar kind of bitumen, known as "Jew's pitch," was exposed in a camera, 
that the parts strongly acted upon by light became insoluble in oil of laven- 
der, while those unacted upon, or influenced by weaker rays, retained their 
solubility in a greater or less degree, and could consequently be dissolved off, — 
thus forming an imperfect picture. This, and other interesting facts, Niepce 
laid before the Eoyal Society of Great Britain in 182*7, but they attracted little 
attention, and in 1829 he formed a partnership with a French artist by the 
name of Daguerre (who was engaged in experimenting on the same subject), 
for the future joint prosecution of their investigations. Niepce died in 1833, 
but Daguerre continued his experiments, and in 1839 first exhibited, as the 
result of his labors, the pictures since called in his honor Daguerreotypes. 
His process was at first kept secret, but was soon purchased by the French 
Government and made known to the world — a pension of 6,000 francs being 
awarded to Daguerre, and one of 4.000 to the son of Niepce. It is also a 
very singular fact, that substantially the same results made known by 
Daguerre, were also discovered at about the same time by Mr. Talbot, an 



* The influence of light in producing the coloration of fruit may he very prettily illus- 
trated by pasting letters cut in paper upon the surface of a ripening peach exposed to the 
Bun. After the lapse of a few days the characters will he found, on removing the paper, 
to he distinctly marked in white, on a red, or yellow ground. 



Questions. — What is photography? Upon what does the art depend? What wera 
some of the earliest photographic experiments? What were Niepce' s experiments? 
Under what circumstances was the daguerreotype process discovered and made known ? 



398 INORGANIC CHEMISTRY. 

English gentleman, who had been engaged in investigating the chemical re- 
lations of light for a number of years previous. 

662. Daguerreotype Process .—The essential features of the 
daguerreotype process, as discovered by Daguerre and now practised, are as 
follows : a highly -polished tablet of silver (copper-plated) is selected as the 
basis of the picture, and exposed to the vapor of iodine. The iodine rapidly 
attacks the silver, and forms over its surface a thin yellow film of iodide of 
silver, which is so exceedingly sensitive to the action of light, that it is almost 
instantly decomposed by it* The plate thus prepared, and carefully pro- 
tected from the light, is then exposed to the image formed by the lens of 
a camera obscura. Relatively the quantity of the light-producing principle, 
and the quantity of the chemical principle reflected from any object are the 
same; therefore, as the fight, and shadows of the luminous image vary, so 
will the power of producing change upon the plate vary, and the result will 
be the production of a picture which will be a faithful copy of nature, with 
reversed lights and shadows; the fights darkening the plate, while the 
shadows preserve it white, or unaltered. The time required for producing 
the impression may vary from 1 to 60 seconds, according to the brightness or 
clearness of the atmosphere, and the time of day. 

If the picture thus formed were left without further care, it would soon 
fade away, and no trace of it would appear on the surface of the plate. In 
practice, the plate is not exposed to the influence of fight sufficiently long to 
form upon its surface an image visible to the eye, but the picture is developed, 
or brought out and rendered permanent, by exposure to the vapor of mer- 
cury. This metal, in a state of very fine division, is condensed upon and ad- 
heres to those portions of the surface of the plate which have been affected 
by the light. "Where the shadows are deep, there is scarcely a trace of mer- 
cury ; but where the lights are strong, the metallic dust is deposited of con- 
siderable thickness. This deposition of mercury essentially completes and 
fixes the picture. 

The reason why the vapor of mercury attaches itself only to those portions 
of the plate which have been affected by the chemical influence of light is not 
definitely known : in all probability, we have involved the action of several 
forces. It is not, however, necessary that a surface should be chemically pre- 
pared to exhibit these results. A polished plate of metal, a piece of marble, 
of glass, or even wood, when partially exposed to the action of light, will, 
when breathed upon, or presented to the action of mercurial vapor, show that 
a disturbance has been produced upon the portions which were illuminated ; 
whereas no change can be detected upon the parts kept in the dark. 

The next step of the process is to remove from the plate any iodide of 
silver which may remain unacted upon, and which would be liable to change 



* Bromine forms a coating even more sensitive than iodine, and is now extensively used 
in its place. 

Questions.— What is the first step of this process ? What the second ? Why does the 
vapor of mercury develop the picture ? What is the concluding part of the process ? 



PHOTOGRAPHY. 399 

on exposing the plate to light. This is effected by dipping the plate into a 
solution of hyposulphite of soda, which dissolves off all the remaining sen- 
sitive coating. The plate is protected to some extent from mechanical in- 
jury, and a richer and warmer effect given to the picture, by covering it with 
a very delicate film of reduced gold. This is accomplished by dipping the plate 
into a solution of chloride of gold, and heating it over the flame of a spirit- 
lamp. 

The surface of the plate is rendered uneven by the operation of light upon 
it, so that it admits of being copied by the process of elcctrotyping. 

663. Paper Photographs . — The plan of obtaining permanent pho- 
tographic images upon paper was originally devised by Mr. Talbot of En- 
gland in 1839. The process first followed consisted in soaking ordinary 
writing-paper in a weak solution of common salt, and when dry washing it 
over on one side with a solution of nitrate of silver. This operation was 
performed by candle-light, and the paper dried by a fire. The sheet thus 
prepared, when laid under an engraving or leaf, and exposed to diffused 
daylight for a period of about half an hour, receives a fair impression, with 
the lights and shadows reversed. The picture thus formed is preserved 
from further change by immersing it in a solution of salt. 

664. T a 1 b t y p e . — In 1841, Mr. Talbot invented the process known as 
the Talbotype, or Calotype, which is essentially the plan at present followed 
in obtaining photographs on paper by the camera. The paper (smooth writ- 
ing-paper) is first brushed over with a solution of nitrate of silver, and then 
immersed in a bath of iodide of potassium. In this way a surface of iodide 
of silver upon paper is prepared, which is not of itself sensitive to the ac- 
tion of light. These operations may be conducted in diffused daylight, and 
a stock of paper may be prepared at once and kept for use. In order to 
render the paper sensitive to the action of light, it is washed over with a 
mixture of nitrate of silver with gallic and acetic acids, and then exposed 
in the camera. Unless the light is very strong, the paper when withdrawn 
exhibits no image, or a mere outline, but the compound has undergone a 
very remarkable change ; for if the blank sheet be washed over with the 
mixture of nitrate of silver with gallic and acetic acids, and then gently 
warmed, an image appears with wonderful distinctness and fidelity, the por- 
tions exposed to the strongest lights assuming the darkest tints. The de- 
velopment of the image in this process appears to be due to the reducing 
agency of the gallic acid, which acts more rapidly upon those portions of the 
surface which have been most freely exposed to the action of light. The dor- 
mant picture may be developed many hours, or even days after it has been 
produced, provided the paper be kept in the dark. It seems as though the 
light, without actually producing a decomposition of the particles of the sil- 
ver salt upon which it falls, gives to them a peculiar condition of unstable 
equilibrium, which predisposes to decomposition when acted upon by a re- 

Questions. — What was the original process for obtaining paper photographs ? Describe 
the Talbotype. 



400 INORGANIC CHEMISTRY. 

during agent like gallic acid. The picture is preserved in this instance, as 
in most others, from future change, by dissolving off the exciting. agents by 
solutions of the hyposulphites. — Miller. 

As silver tablets are expensive, and paper somewhat unreliable, glass 
coated with a sensitive substance has been extensively introduced as a ma- 
terial for receiving the photographic images. Glass is chiefly prepared for 
this purpose in two ways ; by coating it with a thin film of albumen containing 
iodide of potassium (the albumen process) ; or by coating it with collodion, con- 
taining iodide of potassium (the collodion process).* The surfaces thus formed, 
when dried and washed with a compound of silver, are ready for exposure 
in the camera. The collodion film can be rendered so sensitive to light, that 
a perfect picture can be formed upon it by an exposure continuing for less 
than one second of time. In what are called ambrotypes, the picture is first 
formed upon a film of collodion and then varnished with a solution of bal- 
sam, which is thought to render the image more distinct. 

Although the agents indicated are the ones chiefly employed in phot- 
ography, recent researches have shown that nature abounds in materials sus- 
ceptible of photographic action. Preparations of gold, platinum, mercury, 
iron, copper, tin, nickel, manganese, lead, potash, etc., have been found more 
or less sensitive, and capable of producing pictures of beauty and distinctive* 
character. The juices of many plants and flowers have also been put into 
requisition, and papers impregnated with them have been made to receive 
delicate, though in most cases, fugitive images, f Attempts have also been 
made, with a considerable degree of success, to cause the light not only to 
draw, but also to engrave the image upon a prepared basis, in such a way 
that the surface may be used for printing. 

665. Photographs in Colors . — All attempts to produce photo- 
graphs in their natural colors have as yet been, on the whole, unsuccessful, 
although a partial success has, in some instances, been attained to. The cir- 
cumstance that the rays by which photographic effects are produced are dark 
rays, entirely distinct from the rays constituting color, would appear, a priori, 
unfavorable to a successful result. 



* Albumen is prepared for this purpose by beating up the -white of eggs -with iodide of 
potassium. Collodion mixture is formed by dissolving gun-cotton in ether, and adding 
iodide of potassium. 

t The terms which have been applied to designate the effects resulting from the use of 
various materials arc very numerous. Thus we have the Chrysotype, in which salts of 
iron and gold are used ; Cyanotype, in which impressions are produced by salts of iron, in 
conjunction with those of cyanogen ; Anthotype, iu which juices of the poppy, rose, etc., 
are employed, and many others. 

Questions, — What materials have been substituted as a basis for photographic action in 
place of silver and glass ? What are the albumen and collodion processes ? What is an 
ambrotype ? Is photographic action restricted to a few substances ? Illustrate this faot. 
What is said of photographs in colors ? 






^30 



JJ I 




ORGANIC CHEMISTRY 



Organic Chemistry is that department of science which 
treats of the chemical nature and relations of those sub- 
stances which are derived, either directly or indirectly, 
from organized beings, — animal or vegetable. 



CHAPTER XVI. 

NATURE OF ORGANIC BODIES. 

666. Composition of Organic Substances. — The number 
of elements which enter into the composition of organic substances is ex- 
tremely limited, the great bulk of all of them being made up of carbon, hydro- 
gen, oxygen, and nitrogen, with which are generally associ ited extremely 
small quantities of sulphur, phosphorus, iron, and a few other elements. The 
infinite differences of appearance and properties which organic substances 
manifest, is due either to a variation in the number of the combining atoms 
of their constituent elements, or to a variation in the grouping or arrangement 
of the constituent atoms as respects each other. 

Thus, for example, vinegar differs from alcohol only in containing a little 
more oxygen and a little less hydrogen, while the proportion of carbon is the 
same in both ; the change of properties, which is occasioned by this slight 
change in compostion, is, however, exceedingly great ; on the other hand, the 
most careful chemical analysis reveals no difference in the composition of 
woody-fiber, starch, and gum, each consisting of precisely the same elements 
united in the same proportions. The difference in properties in this case, is 
supposed to be due to a difference in the grouping of the atoms, somewhat 
as is represented in Figs. 205, 206, 20?. 




Qttestio>'8. — What is organic chemistry ? What is said of the composition of organic 
compounds ? How arc so many different organic compounds produced from so few ele- 
ments ? Illustrate this. 



402 



ORGANIC CHEMISTRY. 



The number of such isomeric bodies in organic chemistry is very 
while their occurrence in inorganic chemistry is extremely rare. 



Fig. 205. 

WOODY FII3EK. 






By far the largest proportion of the substances which make up the struc- 
ture of plants are composed of but three elements — carbon, hydrogen, and 
oxygen. Animal substances, on the contrary, are generally characterized by 
the presence of nitrogen. Bodies which contain nitrogen are designated as 
azoiized compounds ; and those which are wanting in it, as non-azotized com- 
pounds. 

G61. The elements of organic bodies, in uniting with each other, are gov- 
erned by the same laws of combination which regulate the composition of 
mineral or inorganic substances. The manner, however, in which the atoms 
of the constituent elements are associated in the one class of compounds is, 
in general, altogether different from what it is in the other — inorganic com- 
pounds being characterized, for the most part, by a great simplicity of compo- 
sition, while those of organic origin are remarkable for their very great com- 
plexity. Thus water, HO, is composed of 1 atom or equivalent of hydrogen, 
and 1 of oxygen; Sulphuric acid, S03, of 1 of sulphur and 3 of oxygen; hy- 
drochloric acid, II CI, of 1 of hydrogen and 1 of chlorine, etc. On the other 
hand, alcohol consists of 4 atoms, or equivalents, of carbon, 6 of hydrogen, 
and 2 of oxygen, its composition being represented by the formula C4II6O2;- 
and ordinary sugar, of 12 atoms of carbon, 11 of hydrogen, and 11 of oxygen, 
or CijjHnOn. The composition of stearic acid, the basis of stearine, is also 
represented by the formula C 6 8H 6 g05, and that of fibrine, the principal con- 
stituent of muscular fiber, by C400H310N50O120PS. 

As a consequence of this complexity of composition, organic substances-are, 
as a class, far more unstable and more liable to decomposition from slight 
causes than inorganic substances; — the power to resist the action of disturb- 
ing forces decreasing, as a general rule, as the number of combined atoms or 
equivalents increases. It is also a noticeable fact that all those organic 



Questions. — What organic bodies, as a class, are generally wanting in nitrogen? 
What generally contain it ? In what manner do the elements of compound bodies unite 
with each other ? What are characteristics of the composition of organic and inorganic 
bodies? Illustrate this. What is the consequence of the complexity of the composition 
of organic bodies ? What is a noticeable fact in relation to organic compounds of a high 
order ? 



NATURE OF ORGANIC BODIES. 403 

bodies which discharge high organic functions, as the substance of the brain, 
the nerves, and the blood, have a most wonderfully complex constitution, and 
are susceptible of disorganization from the slightest causes.* 

"When organic substances are decomposed by the action of heat, light, elec- 
tricity, chemical affinity, and even by mechanical action, they do not tend to 
divide into separate and isolated elements, but to form more simple com- 
pounds. Thus 1 (compound) atom of grape sugar, C12H14O14, easily divides 
in 2 atoms of alcohol, 2(C4H 6 0o), 4 of carbonic acid, and 2 of water. If an or- 
ganic body be exposed to an intense degree of heat, with access of air, its 
constituents all unite with oxygen to form gaseous compounds, and it is com- 
pletely consumed — generally after it has been converted into a black, carbon- 
aceous mass. The property of blackening when a body is exposed to heat, 
which is due to the presence of carbon, is a sure characteristic of its organic 
derivation. 

668. Origin of Organic Substances.— Organic sub- 
) stances have their origin entirely in plants. 

The chemist, when he exerts his skill on materials of an organic origin, 
extracts a series of substances, each proceeding from the other, whose com- 
position becomes more and more simple, until it reaches some species known 
to mineral chemistry. Thus, from sugar we may extract alcohol and car- 
bonic acid, and from alcohol water and bi-carbureted hydrogen. In the 
vegetable organization, on the other hand, an operation exactly the reverse 
takes plnce. The living structure takes in air, water, and mineral elements, 
assimilates them, and in virtue of a certain peculiar force, builds them up and 
disposes them into groups of a certain stability — or into organic products. 



( 



* " There is a physical character which will sometimes enahle us to give a good guess 
as to th j simple or complex constitution of an organic substance — the faculty of crystalli- 
zation. The power of assuming, on solidification, a distinct and often very characteristic 
geometrical form, appears to be possessed by all chemical compounds of a definite and 
constant composition, with the exception of a certain number, principally to be found in 
a class of organic substances of the most complicated and unstable nature. We know 
nothing, and apparently at present can know nothing, of the ultimate structure of any 
substance whatever ; but it is not difficult to figure to one's self some idea of the gradual 
weakening of the molecular forces upon which crystallization depends, whatever the na- 
ture of those forces may be, by an increase in their number, and in the multiplicity of 
directions in which the forces themselves are exerted, it very often happens that in those 
cases where crystalline texture is altogether absent, we observe in its place an appearance 
of a very different kind ; — we notice that the smallest particles of matter which can be 
traced by the microscope exhibit a rounded or globular figure instead of the straight lines 
and angles of the crystallizable compounds. These very frequently appear to aggregate 
together in strings, or rows, not altogether unlike some of the very lowest structures of 
the vegetable world, where a commencement of organization is, as it were, just visible. 
The substances forming the chief constituents of the animal body are in this condition." 
— Actoman Pnze Essay, Fownes. 



Questions.— "What circumstances attend the decomposition of organic bodies? What 
property indicates the derivation of an organic substance ? What is the primal origin of 
all organic substances ? Illustrate this. Do animal structures create organic products ? 



404* ORGANIC CHEMISTRY. 

The force by which this result is brought about is called the vital or life force ; 
but we know nothing of its nature, and recognize it simply by its effects. 

Qrganic substances thus originated pass into the systems of animals, which 
possess no power of creating or forming the materials which compose their 
structures, and can only consume and transform that which is supplied to them 
by plants. 

Man has never yet been able to artificially make an organic body ; by 
which assertion we mean to be understood, that he has never been able to 
take the single or dead elements, and cause them to unite at will so as to 
form compounds like those produced through the agency of animal or vege- 
table life. Chemists are, however, able to transform one organic body into 
another, or to unite materials derived from substances already organized into 
compounds possessing characters entirely different from those of their con- 
stituents. Thus, starch may be transformed into sugar, and sugar into the 
acid of ants (formic acid) ; some of the essential oils have also been produced 
artificially, and within the last few years (1855), Bertholet, an eminent French 
chemist, has succeeded in making alcohol from sulphuric acid, water, and bi- 
carburetted hydrogen.* 

669. Compound Radical s. — It has been already shown that cyano- 
gen and ammonium, compound bodies, comport themselves in every respect 
like radicals, or elements. In organic chemistry many such compound radi- 
cals are recognized, some consisting of two elements, carbon and hydrogen, 
and some of three or four, carbon, hydrogen, oxygen, and nitrogen. Some, 
like cyanogen, correspond in properties to the metalloids ; others, like ammo- 
nium, resemble the metals, and both by uniting with oxygen, chlorine, and 
acids, form oxyds, chlorides, and salts. Each, also, by the addition or group- 
ing round it of other molecules, constitutes the root or basis of a whole class 
or series of compounds. 

Thus, for example, carbon unij.es to hydrogen in the proportion of 4 atoms 
of the former to 5 of the latter, C4H5, to form a radical called Ethyle. Ethyle 
oxydated, forms oxyd of ethyle, or ether, C4H5+O ; oxyd of ethyle plus an 
atom of water, forms hydrated oxyd of ethyle, C 4 Il5,0,HO, or alcohol, the 
formula of which is generally written C4II6O2 ; ethyle, plus an atom of chlo- 
rine, forms chloride of ethyle, C^HsjCl, and if sulphur be substituted in the 
place of chlorine, we have sulphide of ethyle, C4H5,S; and in this way, by 



* The muscles of animals and the fiber of wood consist of distinct chemical compounds, 
which the chemist has been able to isolate and 6tudy, but not to imitate. It is hoped, and 
expected by some, that the power will ultimately be attained to of artificially forming 
those products which, in the form of meat, cotton, flax, etc., are so essential to the wel- 
fare of man. The advocates of the possibility of such a result find some support for their 
views in the fact that two organic bodies, cyanogen and ammonia, are undoubtedly formed 
artificially in the workings of blast-funsaces, but in what manner it is impossible at 
present to explain. 

Questions. — Can we artificially accomplish this ? What power do we possess ? What 
are compound radicals ? What is the character of the radicals recognized in organio 
chemistry ? Illustrate how classes of compounds are formed from such a basis ? 



VEGETABLE TISSUE. 405 

the continued addition or subtraction of elements, a great variety of compound 
bodies may be formed, all referable to one central radical. Ethyle itself may 
be also obtained from its oxyd, as potassium is derivable from oxyd of po- 

\ tassium, or potassa, although by a different process. 

\ The discovery and recognition of these compound radicals has greatly 
facilitated the progress of organic chemistry, and has rendered it possible to 
classify and arrange in groups a great number of bodies, which from their di- 
verse properties would seem to have no connection with each other. Thus, 
the fats, the oils, the resins, the alcohols, the ethers, with many coloring, 
odoriferous, and medicinal substances, are now grouped and studied as de- 
rivatives from various central radicals, and not as independent principles. 
There are, however, many organic substances of great importance, the radi- 
cals of which have not yet been discovered. 



CHAPTER XVII. 

ESSENTIAL IMMEDIATE PRINCIPLES OF PLANTS. 

670. By the essential immediate principles of plants, we understand those 
substances which the plant appears to form, through the agency of the vital 
force, directly from the inorganic elements obtained from without ; or those 
principles which mainly constitute the structure, in a greater or less degree, 
of all plants, and are essential to their existence. 

These substances are also often spoken of as the proximate principles of 
plants, and are conveniently divided into two classes, viz., those which con- 
tain nitrogen, as albumen, gluten, vegetable casein, etc., and those which are 
destitute of this element, as vegetable tissue (woody-fiber), starch, gum, sugar, 
etc. The separation of an organized substance into its proximate substances, 
or principles, is called its proximate analysis ; and its separation into its final 
or simple elements, its ultimate analysis. 

In the consideration of the two classes of the proximate principles of 
plants, it is most convenient to commence with those which do not contain 
nitrogen as a constituent element. 

SECTION I. 

VEGETABLE TISSUE, STARCH, GUM, SUGAR, ETC. 

671. Organic Structure . — Since the discovery of the microscope, 
unwearied efforts have been made to ascertain the manner in which dead 
and inert inorganic elements unite to form organized and living . structures. 

Questions. — What do we understand by the essential immediate principles of plants ? 
Into what two classes are the proximate principles of plants divided? "What is "under- 
stood by a proximate and an ultimate analysis ? 



406 



ORGANIC CHEMISTRY. 




Fig. 208 



'^ZJ 



209. 



The result of all inquiries have terminated in the establish- 
ment of a single fact, viz., that the lowest primary form 
of organization we can detect, whether of the individual 
(animal or vegetable) or of its parts, is a cell — a little glob- 
ular or oval body, membranous or solid externally, fluid 
within. (See Figs. 208, 209, 210.) Beyond this we can 
not go, or say how it is that the elementary particles of 
matter are led to assume this form ; but the appearanco 
of cells always precedes the formation of circulating ves- 
sels, or any of the more complex forms of organic struc- 
ture. 

Cells once formed, multiply in number by division' (seo 
Figs. 209, 210), and by the introduction of new matter 
from without, and thus it is that all growth, or increase in 
volume and weight, in all animals and vegetables, takes 
place ; and an animal or plant is a structure " built up 

of individual cells, 
Fig. 211. somewhat as a 

house is built of 
bricks." Fig. 211 
represents a mag- 
nified view of the 
cellular tissue of a 
rootlet. 

672. The natural 
figure of a cell is 
globular, but under 
varying circum- 
stances it may as- 
sume a great variety 
of forms. The hairs on the surface of plants are cells drawn out into tubes, or 
are composed of continuous rows of cells. Cotton consists of simple long 
hairs on the coat of the seed ; and each of these hairs is a single cell. Fig. 
212 is a microscopic appearance of a section of the stalk of the calla, showing 
the arrangement of the cells, with passages between them.* 





* The size of the common cells of plants varies from about the thirtieth to the thou- 
eandth of an inch in diameter. An ordinary size is from l-300th to 1 -500th of an inch in 
diameter ; so that there may he generally from 27 to 125 millions of cells in the compass 
of a cubic inch. Now when it is remembered that many stems of plants shoot up at 
the rate of an inch or two a day, and sometimes of three or four inches, we may form 
some conception of the rapidity of their formation. When a portion of any young and 
tender vegetable tissue, such as an asparagus root, is boiled, the elementary cells sepa- 
rate, or may be readily separated by the aid of fine needles, and examined by the micro- 
Ecope. — Ghay. 



Qttestions. — In what form does organization first manifest itself? What is a cell! 
How do plants and animals grow and increase ? What is the natural figure of cells ? 



VEGETABLE TISSUE. 40T 

613. A living cell possesses a wonderful power of influencing chemical 
action ; and what is called " secretion''' in animals and plants is the result 
of the exercise of this function. By means of it, the cell first draws in or 
secretes inorganic matter, and then organizes it, or fits it into its own struc- 
ture. Different cells manifest very different powers ; for example, one kind 
of cell will decompose carbonic acid, reject the oxygen, and preserve the car- 

FiG. 212. 




bon within its walls or tissues ; another will produce out of the inorganic con- 
stituents of the air the odoriferous principle of the rose ; a third will convert 
a portion of blood into milk ; and. yet to the eye they are all alike, "a collec- 
tion of little wet bladders." 

614. Cellulose, or Cellular Tissue, C 12 Hi 0i . — The mate- 
rials of which the walls of the cells of plants is composed is termed in chem- 
istry cellulose, or cellular tissue. It consists of three elements, carbon, hydrogen, 
and oxygen, and has the same composition, when pure, in all plants. It is 
distinguished among all the substances which enter into the composition of 
plants by its great resistance to chemical agents — a resistance which allows 
its separation in a state of purity. 

Cellulose is nearly pure in cotton, and in the fibers of the flax and hemp- 
plants, also in paper and old linen and cotton cloth. The difference between 
cotton and flax is due simply to a difference in the mechanical construction of 
their fibers ; the fiber of cotton being a flattened tube or hollow ribbon with- 
out joints, and with pointed or rounded ends ,• while the fibers of flax and 
hemp consist of rounded tubes (cells) bundled or jointed together in parallel 
directions, and easily separable into shorter and more minute filaments. 
Cotton fibers have what is called a staple ; that is, they are all of the same 
length, and are, therefore, easily spun by machinery ; flax and hemp fibers 
are. on the contrary, irregular in length, and are more rigid than cotton, and 
can not be so easily twisted into fine, regular threads. Fig. 213 represents 
the microscopic appearance of cotton, and Fig. 214 that of flax. 

Cellulose is insoluble in water, alcohol, ether, and dilute acids. By treat- 

Questions What property do cells possess? Illustrate this. "What is cellulose? 

By what other name is it known ? In what substances is it nearly pure ? What consti- 
tutes the difference between flax and cotton ? What is meant by the staple of cotton ? 
What are the properties of cellulose ? 



408 



ORGANIC CHEMISTRY, 








ing sawdust successively with warm water, alcohol, ether, alkalies and ac;ds, 
Fig. 213. we ma y remove frota the -p lG 214 

wood all its soluble constitu- 
ents, and obtain cellulose in 
a pure condition. By con- 
tinued contact with chlorine, 
acids, and alkalies, cellulose 
is, however, gradually de- 
composed and destroyed. 

6 15. Gun-cotton, 
Pyroxyline. — When cellu- 
lose is subjected to the ac- 
tion of nitric acid, or to a 
mixture of nitric and sul- 
phuric acids, it gives up a 
portion of its hydrogen and 
oxygen (as water), and receives nitric acid in place — -becoming transformed 
thereby, without change of physical appearance, into an explosive substance 
which is known as gun-cotton, or pyroxyline. 

The process by which gun-cotton is formed is essentially as follows : per- 
fectly clean cotton is soaked for about five minutes in a mixture composed 
of 1 part concentrated nitric acid, with 2 parts concentrated sulphuric acid ; 
it is then removed, carefully washed with water from every trace of acid, 
and dried by exposure to the air. As thus prepared, it retains the appear- 
ance of cotton, but inflames instantaneously when touched with a hot wire or 
lighted match, and when struck with a hammer upon an anvil, explodes 
with great violence. "When used in fire-arms, it acts like gunpowder, but its 
explosive force is at least four times greater than that of powder, and it does 
not, moreover, foul the gun to the same extent as the latter substance. Its 
liability to burst the gun and to accidental explosions has, however, caused 
its rejection for most practical purposes, and in experimenting with it too 
great caution can not be exercised. By subjecting starch and sugar to treat- 
ment with nitric acid, other explosive substances analogous to gun-cotton 
may be formed. 

616. Collodion . — Gun-cotton is insoluble in both water and alcohol ; 
it dissolves sparingly in pure ether, but readily in ether containing a small 
percentage of alcohol. Its ethereal solution constitutes a syrupy liquid which 
yields by evaporation a thin, transparent, powerfully adhesive substance, in- 
soluble in water. This product, which has received the name of collodion, 
is advantageously used as a substitute for court-plaster for the covering of 
wounds, and also as a sensitive basis for the reception of photographic pictures. 
611. Parchment Pape r. — When paper is exposed to a mixture of 



Questions. — What is the action of nitric acid upon cellulose ? What is the process of 
making gun-cotton ? What are its properties ? What is collodion ? What action does 
sulphuric acid hare upon paper ? 



VEGETABLE TISSUE 



409 



2 parts concentrated sulphuric acid (s.g., 1-854, or thereabouts) with 1 of water, 
for no longer time than is taken in drawing it through the acid, it is imme- 
diately converted into a strong, tough, skin-like material, to which the name 
u parchment jxiper" has been applied. All traces of the sulphuric acid must 
instantly be removed by washing. If the strength of the acid much exceeds 
or falls short of the limits named, the paper is either charred or transformed 
into other compounds. By this treatment, in a little more than a second of 
time a piece of feeble, porous, unsized paper is rendered so strong, that a 
ring seven eighths of an inch in width is said to be capable of sustaining a 
weight of 90 lbs. The nature of the change thus effected is not understood, 
the chemical composition and weight of the paper remaining unaltered. It 
is, however, somewhat contracted in dimensions, is not affected by water like 
common paper, and is not decomposed by heat and moisture like common 
parchment. 

678. L i g d i n e . — As the growth of the plant continues, the walls of the 
cells constituting the cellular tissue generally become incrusted on their in- 
terior surfaces with a substance formed from the organic matters dissolved 
in the sap. This substance constitutes the principal part of the weight of 
wood (lignum), and is chemically known as lignine. It grows thicker with 
the age of the plant, and finally fills up the cells, Fig-. 215. 
leaving, however, minute pores or conduits for the 
circulation of the sap. Fig. 215 represents a mi- 
croscopic section of wood-cells of the birch, nearly 
filled up by regular depositions of lignine. The 
difference between the heart-wool and sap-wood, 
or external wood, of a tree, is duo simply to the 
fact, that the cells of the center are the oldest, and 
consequently are more densely and compactly filled > 
with ligneous matter than those which have been 
formed later, and constitute the exterior of the tree. 
It is by this thickening of the cells that the skins 
of fruits and the shells of nuts acquire their hard- ^ 
ness, and it is simply through variations in the continuance of this process, 
and in the nature of the materials deposited, that all the different appearances 
of wood originate ; the coloring and resinous matters of wood being deposited 
in connection with the lignine. 

Lignine can not be isolated in a state of purity ; it is supposed to dif- 
fer somewhat from cellulose, or the original cell membrane, in containing a 
little more hydrogen and carbon ; it is, therefore, richer in combustible mat- 
ter. 

679. Destructive Distillation of Wood , — When wood is sub- 
jected to heat in close vessels (distillation), or with a partial access of air, a great 

Questions. — Describe the process for preparing parchment paper. What is lignine ? 
What constitutes the difference between the heart-wood and sap-wood of a tree ? What 
are other illustrations of the formation of lig:iine ? What is said of the chemical compo- 
sition of lignine ? 

18 




410 ORGANIC CHEMISTRY 

variety of products are obtained, which are characterized by singularly differ- 
ent properties. The principal of these are charcoal, which is not volatile, 
and remains behind, illuminating gas (carburets of hydrogen), carbonic acid, 
water, pyroligneous acid, and a resinous substance known as " wood-tar." 
Of these several substances, the two last mentioned only remain unconsid- 
ered ; they are extensively used in the arts, and are obtained upon a large 
scale by distilling wood in iron cylinders. 

680. Pyroligneous Acid, sometimes called wood vinegar, is a brown 
acid liquid, having a strong smoky taste and flavor. It is obtained most 
abundantly by the distillation of dry beach-wocd — a pound of wood yielding 
nearly one half pound of acid. Its uses and chemical composition will be 
hereafter noticed. 

681. Creosote is a colorless, oily fluid, obtained from pyroligneoua 
acid and wood-tar. It possesses a peculiar penetrating odor of smoke, and 
when applied to the skin of the mouth or tongue, acts as a cautery. 
Creosote is one of the most powerful antiseptic agents known in chemistry. 
Hence the etymology of its name, from the Greek Kpeoc, flesh, and gu^u, 1 
preserve. Meat steeped for about 24 hours in a solution of 1 part of creosote 
to 100 of water, is rendered incapable of putrefaction, and acquires a delicate 
flavor of smoke. It is indeed the presence of this principle in wood-smoke 
which gives to the latter its characteristic smell, its property of causing lach- 
rymation, and its power of curing meats and fish. Creosote diluted with 
alcohol is often employed for relieving toothache arising from putrefactive de* 
cay in the substance of the tooth, and as a styptic for checking hemorrhage. 
"When taken internally in any quantity it is a corrosive poison, but a very 
dilute solution is sometimes given in medicine. It is also extensively em- 
ployed by liquor manufacturers for imparting the peculiar smoky flavor to 
what is called "Irish whiskey." 

682. Tar. — There are several varieties of tar. The kind so largely em- 
ployed in the arts, as in ship-building, is obtained by subjecting to a rude 
process of distillation the roots and wood of the resinous pine ; another va- 
riety of tar is obtained from the destructive distillation of hard wood ; and a 
third from the destructive distillation of coal (coal-tar). 

"Wood-tar is insoluble in water, but soluble in alcohol, and is extremely 
rich in carbon, which gives it in part its black color. When applied to wood 
it exerts a preservative action by reason of the creosote it contains, and 
also by preventing the penetration of moisture. On distillation, it separates 
•into a volatile oil (oil of tar) and a non-volatile substance, pitch. 

From oil of tar a great number of products may be extracted, all of which 
are compounds of carbon and hydrogen. One of these, called eupion, an 

Questions.— What are the products which result from the distillation of wood ? "What 
is said of pyroligneous acid ? What of creosote ? To what are the peculiar properties 
of smoke due? What is said of the antiseptic influence of creosote ? What are the uses 
of creosote? What is common tar the product of? What are the three varieties of tar? 
What are the properties of wood-tar ? What are its products of distillation ? What is 
said of the products of the distillation of oil of tar ? 



VEGETABLE TISSUE. 411 

oily, fragrant substance, is the lightest of all known liquids. Another, pa- 
rafine, is a white, crystallizable substance, closely resembling spermaceti in 
appearance. 

Coal-tar is a mixture of solid and liquid hydrocarbons, and is formed abun- 
dantly in the production of illuminating gas from coal, which is a vegetable 
substance. It was formerly regarded as a useless product, but within the 
past few years it has been rendered valuable by the discovery of economical 
methods of separating it into its constituents. This is principally effected by 
distilling at different and carefully regulated temperatures, and condensing 
the distillates in the order of their volatility. 

The first product of distillation is a limpid, oily liquid, called benzole. It 
closely resembles oil of turpentine in appearance and odor, and is highly 
volatile and inflammable. A current of moist air passed through benzole 
becomes so thoroughly and permanently impregnated with its vapor, that it 
may be conveyed away in pipes and burned as an illuminating gas. The 
application of this property of benzole constitutes the essential feature of the 
so-called "portable gas generators." Benzole is also used to a considerable 
extent as a most ready and cheap solvent for various resins, camphor, the 
essential oils, grease, wax, India rubber, and gutta-percha. 

The second important product of the distillation of coal-tar is a heavy oil, 
not readily volatile at ordinary temperatures. It is known as " coup" oil, or 
heavy oil of coal-tar, and is extensively used for the lucubration of machinery, 
and for illuminatng purposes. 

Similar oils may also be obtained in much larger quantity and more cheaply, 
by directly distilling the richer varieties of bituminous coal : the products 
known as " Breckenridge coal oils" being produced in this manner. In addition 
to these oils, both coal and coal-tar also furnish by distillation a great variety 
of other products ; among which are a white volatile solid called napthaline, 
somewhat resembling camphor in appearance, and exhaling a faint, but 
agreeable odor, and several less volatile wax-like substances, which have 
been employed to some extent for the manufacture of candles. 

Coal-tar, mixed with gypsum, gum shellac, and other substances, forms a 
water-proof and durable material for the covering of roofs. By subjecting 
the products of coal and coal-tar to the action of chlorine and the acids, an 
almost endless variety of curious compounds may be generated, some of which 
have important industrial applications. Benzole distilled with nitric acid, 
yields a highly fragrant substance (nitro-benzole), so closely resembling the oil 
of bitter almonds, that it has almost entirely superseded the latter in the pre- 
paration of perfumery and the scenting of soaps. The heavy oil may also be 
converted by treatment with the same acid into a beautiful lemon-yellow, 



Questions. — What is coal-tar ? By what process are the constituents of coal-tar sepa- 
rated ? What is the first product of its distillation ? What are the properties of benzole ? 
What are its uses? What is coup oil? What are some of the other distillates of coal? 
From what other source beside coal-tar may these products be obtained? What is said 
of the compounds artificially formed from the distillates of coal ? 



412 



ORGANIC CHEMISTRY. 



crystalline substance (caroazotic acid\ which is capable of imparting to silk 
and wool a brilliant yellow color. 

683. Mineral Oils, Petroleum, Naphtha, etc. — Oils similar hi composi- 
tion and properties to those obtained from the distillation of coal, are observed 
to issue from the earth in many localities, and often in considerable abundance. 
They are supposed to be generated by the action of internal heat upon beds 
of coal, or upon rocks rich in bituminous matter. The nature of these oils 
differs greatly — the thinner and purer varieties being generally called naphtha, 
and the more viscid liquids petroleum. The most abundant localities of these 
substances are in Persia, in the vicinity of the Caspian sea, in Italy, and in 
Birinah. They are also found in many places in the United States — the well- 
known " Seneca oil," found in the vicinity of Seneca Lake, N. Y., being a 
product of this character. At Baku, in Persia, extensive beds of marl exist 
which are saturated with naphtha, and in some parts of this district so much 
combustible gas or vapor issues from the ground, that it is used by the in- 
habitants for cooking, and by certain religious sects for the maintenance of 
a perpetual fire. Naphtha is somewhat used in the arts in the preparation 
of varnish, as a solvent for certain resins and India-rubber, and by the chemist 
as a means of preserving the metallic bases of the alkalies — potassium and 
sodium — from oxydation. 

684. A s p h a 1 1 u m — Mineral Pitch, Bitumen — is another natural product 
undoubtedly derived from the decomposition of organic matter. It is a black 
solid, closely resembling petroleum, and melts at about 212° F. It is found 
abundantly in many localities, especially in the vicinity of the Dead Sea and 
in the island of Trinidad, W. I., in which latter place it constitutes a lake 
three miles in circumference and of an unknown depth ; — the pitch lake of 
Trinidad. 

685. Contents of the Cells of Plants .—The contents of the 
cells of plants comprise all the immediate products which plants produce. 

Growing and vitally active cells are filled with liquid ; completed cells may 
still be filled with liquid or with air, or with solid matter only. The liquid 
contents of the vegetable tissues, are generally spoken of as sap ; but this 
term does not specially refer to any particular substance. Sap, in the first 
instance, is water impregnated with certain gaseous matters (carbonic acid, 
ammonia, etc.) and a minute quantity of mineral salts, which are imbibed by 
the roots of the plant from the soil, and carried upward through the stem. 
It is, therefore, in the first instance, inorganic in its nature. As, however, 
it traverses the cells of the plant, it mingles with the soluble assimilated 
matters which these contain, and becomes changed in character, so that un- 
mixed, crude sap, is never met with in the plant. On reaching the leaves, 
it becomes farther transformed, under the influence of light, into organizable 
matter, or into matter capable of being assimilated by the cells and converted 



Questions. — What are mineral oils ? What names are generally applied to these pro- 
ducts ? What is said of their natural occurrence ? What are the uses of naptha ? What 
is asphaltum ? Where is it found ? What are the contents of the cells of plants? What 
is sap ? Describe the successive transformations of sap ? 



VEGETABLE TISSUE 



413 



into organic products. From the sap thus elaborated, the cell manufactures, 
or secretes, all the constituents of the plant. 

Of the non-azotized substances secreted by the plant cells, the most abun- 
dant and widely distributed is lignine, which has been already described. In 
addition to this, three other substances, starch, gum, and sugar, closely allied 
to lignine in composition, are secreted in greater or less abundance by al- 
most all plants. 

686. Starch, Ci 2 H 10 0i . — This substance presents to the naked eye the 
appearance of a white'powder, but when viewed under a microscope is seen 
to consist of transparent oval or rounded grains, each of which has a dark 
spot at one extremity, with fine concentric rings drawn round it. These 
characteristic appearances are best seen in starch from the potato, with a 
magnifying power of from 250 to 500 diameters. (See Fig. 216.) The mag- 

Fig. 216. Fig. 21*7. 





nitude of the starch grains varies extremely in the different plants, and even 
in the same celL Thus in the potato the largest grains measure from l-300th 
to l-500th of an inch in their larger diameter, but in the smallest only 
l-4400th of an inch. In wheat flour the larger grains are from l-800th to 
l-900th of an inch in diameter. The shape of the grains in the same plant 
or organ is very nearly uniform, but differs greatly in different plants ; so 
much so, that mixtures of various starches may be easily detected by the 
microscope. 

Starch, while an almost universal product of all vegetable cells, is accumu- 
lated more abundantly in some species of plants than in others. In the 
common potato, each individual cell is so completely filled and distended 
with an accumulation of starch mingled with water, that the whole root has 
an appearance of deformity. Fig. 217 represents the manner also in which 
the starch grains fill up the cells of the maize (i. e., in Indian meal). Starch 
is particularly abundant in all cereal grains, in all seeds, in the pith and bark 
of many trees, and in many roots and tubers (as the potato, turnip, carrot 

etc.).* , 


* Wheat flour contains from 39 to 77 per cent, of starch ; rice flour ahout 86 per cent. ; 
Indian meal from 70 to 80 per cent. ; rye flour, 50 to 60 ; buckwheat, 50 ; pea and bean 
meal, 42 ; and potatoes from 13 to 15 per cent of starch, mingled with about 70 parts of 
water. 



Questions. — Beside lignine, what other non-azotized substances are generally contained 
iu the cells of plants? What is the appearance of starch? What is said of the size and 
appearance of its granules ? In what vegetable substances is starch most abundant ? 



414 ORGANIC CHEMISTRY. 

The starch of commerce is usually obtained from potatoes or wheat. The 
essential features of its process of manufacture consist in bruising or grind- 
ing the vegetable structure to a pulp, and then washing the mass with cold 
water upon a sieve. In this operation the torn cellular tissue and some 
other constituents are retained upon the sieve, while the starch granules pass 
through its interstices with the water. From this liquid the starch separates, 
on standing, as a fine white powder. 

Starch is insoluble in water, as its mode of preparation necessarily implies. 
"When, however, a mixture of starch and water is heated to near its boiling 
point, the granules swell, burst, and allow their contents to become mingled 
with the water, producing thereby a nearly transparent, glutinous mass, 
in which the minute shreds of membraneous matter, comprising the cell- walls, 
float. The rounded and swollen appearance which potatoes, peas, rice, and 
most other vegetables assume when boiled, is due to a distension of their 
starch granules through an absorption of water at the boiling temperature. 

The chemical test of starch is jodine, which forms with it a beautiful blue 
compound, insoluble in water. This reaction may be strikingly illustrated 
by adding to a tumbler of pure water a single drop of gelatinous starch, and 
then stirring the mixture with a glass rod moistened with an alcoholic solu- 
tion of iodine. 

The chemical composition of starch is exactly the same as that of cellulose, 
and it appears to be especially the ready prepared material of vegetable fabric, 
which the plant accumulates in cells as a provision for future growth. 

The substances known as sago, tapioca, and arrow-root, are only varieties 
of starch ; the former being obtained from the pith of various species of the 
palm, and the two latter from the roots of certain tropical plants. 

687. Dextrine. — "When thick gelatinous starch is boiled for a few 
minutes with a small quantity of dilute acid, as sulphuric acid, for example, 
it speedily loses its viscidity, and becomes changed into a fluid as thin and 
limpid as water. If the acid be now withdrawn, by saturation with chalk 
(which combines with it to form insoluble sulphate of lime), and the liquid 
be gently evaporated to dryness, it furnishes a substance resembling gum, 
which is termed dextrine.* This new body is freely soluble in cold water, 
and has exactly the same composition as gelatinous starch, but is not colored 
by iodine. 

If, instead of interrupting the action of the acid upon the starch as soon 
as the mixture has become clear and thin, we continue the ebullition for sev- 
eral hours, adding from time to time small quantities of water to supply the 



* Dextrine, so called from the circumstance that when a beam of polarized light is 
passed through its solution, it causes the plane of polarization to turn to the right. 

Questions. — From what sources is it generally obtained ? How is starch manufac- 
tured ? When starch is boiled in water, what takes place ? What is the chemical test of 
starch ? What is its chemical composition ? What is sago, tapioca, and arrow-root ? 
What is dextrine ? How is Btarch converted into dextrine ? How is dextrine converted 
into sugar ? 



VEGETABLE TISSUE. 415 

place of that lost by evaporation, and finally, neutralizing the acid by chalk, 
filter and boil down the clear solution to a small bulk, we obtain a syrupy 
liquid, which on standing for a few days, entirely solidifies to a mass of 
grape-sugar, exceeding in weight the starch from which it was produced. 

How this transformation of starch into dextrine, and dextrine into sugar, 
is effected is not fully understood. The acid empk>3 r ed undergoes neither 
change nor diminution, and if not volatile may be recovered, without loss, after 
the conclusion of the experiment; nothing, moreover, is withdrawn from tho 
air, and no other substances but dextrine and grape-sugar are generated. 
Chemists, therefore, have very generally adopted the conclusion that the acid 
occasions the transformation and change in question by its mere presence, 
and the phenomenon is cited as an example of catalysis. (§ 255, p. 161.) 
Spongy platinum, as has been already pointed out (§ 296), apparently acts 
in a similar manner, and is capable of exciting chemical activity in contiguous 
substances without being itself affected. In the case of the dextrine, as its chem- 
ical composition is precisely the same as that of starch, the difference in prop- 
erties is referred to a change in the arrangement of its constituent atoms of 
carbon, hydrogen, and oxj^gen. In the conversion of the dextrine into sugar, 
the change seems to be effected by a fixation or incorporation into the for- 
mer substance of an additional quantity of the elements of water, hydrogen 
and oxygen — as the sugar thus produced sensibly exceeds in weight the 
starch employed. 

4 688. Diastase . — There are, however, several other methods by which 
these same changes in starch may be effected, in addition to the one noticed. 
Thus, all seeds in the act of germinating, and all buds in developing, pro- 
duce from the nitrogen compounds which they contain a very peculiar sub- 
stance called disastase. This body, which the chemist has never yet been 
able to fully isolate, possesses the same power as the dilute acid of converting 
a large quantity of starch, first into dextrine and then into sugar. Its ac- 
tion, however, takes place at a much lower temperaturo than that of ebul- 
lition. 

This fact may be experimentally shown by mixing a little infusion of malt 
(germinated barley) with a considerable quantity of thick starch paste, and 
subjecting the whole to a gentle heat not exceeding _160° P. In a few min- 
utes the mixture, from the production of dextrine, becomes thin like water, 
and if the temperature be kept up during three or four hours, the liquid will 
be found to have acquired a sweet taste, and to be rich in sugar. The quan- 
tity of dextrine necessary to effect this change is very small — one part in two 
thousand parts of starch being sufficient to entirely convert the latter into 
sugar. A boiling heat coagulates the diastase, and by rendering it insoluble 
destroys its power. 

The well-known sweet taste which fruits and vegetables acquire by freez- 



Questioxs. — What is said of these . transformations ? How do germinative seeds and 
bu^s act upon starch ? What is disastase ? How may its properties be illustrated ? Why 
&> t frozen thawed fruits and vegetables sweet ? 



416 ORGANIC CHEMISTRY. 

ing and thawing, is due to the fact that the starch which they contain 13 
converted, in pari, by the action of the frost, into sugar. 

689. Dextrine is used extensively in the arts as a substitute for gumj i. e., 
for the stiffening and glazing of muslins, in calico-prhitiug, and in the printing 
of wall-papers. It is manufactured for industrial purposes by simply roasting, 
dry potato-starch, or subjecting it to a heat of about 400° F. By this treat- 
ment the starch "acquires a yellowish tint and is rendered soluble in water. 
Dextrine occurs in commerce under the name of " Bri tish gum." 

690. Gum . — In addition to dextrine, which is found in greater or less 
quantity in the juices of every plant, the term gum is generally applied to 
designate certain vegetable substances which possess the same elementary 
composition as starch, and which are soluble in water, but not in alcohol. 
In some plants they exist so abundantly, that they exude from the bark as 
viscid liquids, which subsequently harden into transparent, globular masses. 
Familiar illustrations of this may be noticed on peach and cherry trees. The 
term resin is rightly applied to those hardened vegetable juices only which 
do not soften or dissolve in water, but are soluble in^lcohoL 

The most important gums of commerce are gum arabic, gum Senegal, and 
gum tragacanth. 

Gum arabic is the product of a species of qmevk. which grows abundantly 
in Africa and Arabia ; gum Senegal, the product of a similar tree, -derives 
its name from Senegal, in Africa, the district from which it was originally 
exported. Both of these gums are freely soluble in water, and form with it 
a mucilage much used for paste ; the mucilage yielded by gum Senegal being 
somewhat thicker than that formed by gum arabic. The pure gummy sub- 
stance contained in them may be precipitated from its solution in water by 
alcohol, and is termed wrdbme. 

Gum tragacanth is the product of a shrub found extensively in Asia Minor 
and Persia, and is composed mainly of a substance termed basorine. It swells 
very much in water, and forms a thick adhesive paste, but can hardly be said 
to dissolve in it. It is, however, soluble in caustic alkalies. 

Gum is an essential constituent of the cereals, and of most seeds, and is 
abundant in many vegetables. Wheat flour contains about j£ per cent. ; rye 
flour, 11 ; Indian corn, 2J2j peas, 6;3f kidney beans, 19 ; potatoes, 3JJj 
cabbage, 2& 

691. Mucilage . — Many seeds, as flax seed, and many roots, barks, and 
leaves of plants, as slippery-elm bark, marsh mallow, etc., yield, when di- 
gested with water, gummy and stringy liquids. To such products the gen- 
eral name of vegetable mucilage has been applied, and their chemical com- 
position is believed to be the same as that of starch and gum. 

692. Pec tine, or pectic acid, is a gelatinous substance found in the 

Questions. — What are the uses of dextrine ? What is " British gum ?" To -what other 
substances is the term gum applied ? How does a gum differ from a resin ? What are 
the principal gums of commerce? From whence are they derived ? What are theirgen- 
eral properties ? What is said of the general occurrence of gum as a vegetable product? 
What is mucilage ? What is pectine ? 



SUGAR. 417 

juices of all ripo fleshy fruits, and allied in composition to starch, gum, and 
mucilage. It is the agent which communicates to the juices of fruits the 
property, when boiled (especially in connection with sugar) and cooled, of 
hardening into jelly, and is hence sometimes called " vegetable jelly." 

693. Sugar . — The term sugar is ordinarily used to designate the sweet 
principle of plants. The chemist, however, at the present day applies it to a 
large number of bodies, which differ greatly from one another in their prop- 
erties. Thus we have sugars which are derived from both vegetable and 
animal organisms—sugars which are sweet, sugars which are slightly sweet, 
and some which are destitute of sweetness ; some sugars, also, are capable 
of fermentation, others do not undergo this change ; some are fluid, but most 
are solid. All sugars, however, agree, with perhaps a single exception, in one 
respect — they consist of carbon, hydrogen, and oxygen, with the two latter 
elements united to the former in exactly the proportions which form water. 
\ Sugar exists in greater or less abundance in all plants, and it is from this 
source only that we obtain our supplies. It abounds most in the growing 
parts, in the stems just before flowering, as those of the sugar-cane, maize, 
maple, etc , in pulpy fruits, and in seeds when they germinate. Like starch, 
it appears to., be a material especially intended to subserve the growth and 
nourishment 6&&he plant ; but unlike it, it exists in the plant only in solution. 

All the numerous varieties of sugar may be conveniently arranged in four 
classes, viz., the cane sugars, the grape sugars, the manna sugars, and the 
sugar of milk. 

694 Cane Sugar, C12H11O11 — This variety of sugar includes the sugar 
of the sugar-cane, beet sugar, palm or date sugar, maple sugar, and the sugar 
of the maize and of the fully ripe sorghum. It is also found in many of our 
common meadow grasses, and in the juices of melons, carrots, and turnips. 
Plants which have but little acid in their sap contain for the most part cane 
sugar ; the chemical reason of this is, that cane sugar, by the action of acid 
substances, is gradually converted into grape sugar, even in the interior of 
the growing plant. 

About eleven twelfths of all the sugar extracted for use is obtained from 
the sugar-cane, and the yearly production from this source, over the whole 
globe, has been estimated at 4,500,000,000 lbs. Of this enormous quantity, 
the population of Great Britain are certainly known to consume at least two 
elevenths. The method of manufacturing sugar from the cane (and also from 
the beet) is essentially as follows : the juice extracted from the vegetable 
structure by pressure, is mixed with a small quantity of hydrate of lime 
(slacked lime), and rapidly heated to near the boiling point. The action of 
the lime is twofold : it removes or neutralizes the acid which rapidly forms in 
the fresh juice, and at the same time unites with and precipitates the glutin- 

Questions. — What is its most noticeable property ? What is the ordinary signification 
of the term sugar? Is the term restricted in a chemical sense to any particular sub- 
stance ? In what respect do all sugars agree ? What is said of the natural occurrence of 
sugar? Into what four classes may all sugars be divided? What sugars are included 
under the name of cane sugars ? How is cane sugar manufactured ? Why is lime used ? 



418 ORGANIC CHEMISTRY. 

cms matters contained in the juice. The removal of these latter substances is 
an essential part of the process, as a short exposure to the atmosphere occa- 
sions their fermentation, which in turn converts the sweet juice into a sour 
and spirituous liquid, totally unfit for the manufacture of sugar. The juice, 
after clarification, is rapidly evaporated in open pans to a thick syrup, and 
then run into wooden vessels to cool and crystallize, and finally, when crys- 
tallized, is allowed to drain in perforated casks. The product remaining after 
drainage, is the common raw or brown sugar, while the drainings constitute 
molasses. _J 

695. Molasses is uncrystallizable sugar. It does (not pre-exist in the 
juice of the cane, but is produced at the expense of the crystallizable sugar, 
mainly by the high temperature used in the concentration of the sacchar- 
ine solution. In improved processes for the manufacture of raw sugar, and 
always in the refining of sugars, the boiling of the syrups is conducted in 
what are called "vacuum pans," which are large metallic boilers so con- 
structed that they can be exhausted of air. The boiling point of the syrup, 
owing to the absence of atmospheric pressure, is thus reduced to about 
150° F., and the formation of molasses almost entirely prevented. 

The process of manufacturing raw sugar, although apparently most simple, 
is attended with many difficulties in practice ; so much so, that of the 18 per 
cent, of sugar contained in the cane juice of the West India Islands, not 
more than 6 per cent., or one third of the whole, is usually sent to market in 
the state of crystallizable sugar. 

696. The Refining of Sugar is not generally carried on in connec- 
tion with manufacture of the crude product. It is effected by dissolving the 
brown sugars in water, adding albumen (whites of eggs, or bullocks' blood), 
and sometimes a little lime-water, and heating the whole to the boiling point. 
The albumen, under the influence of heat, coagulates, and forms a kind of net- 
work of fibers, which inclose and separate from the liquid all the mechanically 
suspended impurities. The solution is then decolorized by filtering through 
animal charcoal, concentrated by evaporation in vacuum pans, and allowed to 
crystallize in conical iron molds. The molasses, or drainings which escape 
from refined sugar, by means of orifices opened in the bottom of these molds, 
is sold under the name of Sugar-house Syrup, Stuart's Syrup, etc. The time 
required for the perfect crystallization and separation of the white sugar in the 
molds is from 18 to 20 days, during which period the syrup is frequently 

stirred in order to prevent the formation of crystals of a 

Fig. 218. lar S e size - 

697. Sugar Candy . — When a strong solution of re- 
fined sugar is allowed to evaporate slowly and uninterrupt- 
edly, the sugar separates in the form of large, transparent, 
colorless crystals, having the form of an oblique, six-sided 
prisms. See Fig. 218. In this state it is known as 
" Sugar," or " Eock Candy." 

Questions. — What is molasses ? How is it formed ? How is sugar refined ? What is 
gugar candy? 




SUGAR. 419 

In many parts of Europe, especially in France, sugar is extensively manu- 
factured from the beet root, the juice of which contains about_8j?er cent, of 
cane sugar. At the present time, about 360 millions of pounds of sugar are 
annually obtained from this source on the continent of Europe, or about 7 per 
cent, of all the sugar consumed in the world. 

The amount of sugar annually extracted from the date palm (principally in 
India and the South Pacific), is estimated at 220 millions of pounds; while 
the quantity annually obtained from the sugar maple of North America is 
about 45_million pounds. 

698. When cane sugar is heated to about 400° E., it gives up two equiva- 
lents of hydrogen and oxygen (water), and is converted into a dark-brown 
substance, termed caramel. This body is freely soluble in alcohol and water, 
and is extensively used for the coloration of spirits — the color of all dark 
brandies being due to it. 

699. Grape Suga r. — Glucose; Sugar of Fruits, C12H14O14. — This var- 
iety of sugar includes the sugar of grapes, of ripe fruits, of honey, and of seeds; 
together with the sugars artificially produced from starch and woody fiber. 
It is more generally diffused in nature than cane sugar, and is the product of 
most plants which contain acids or sour juicos. 

The white coating upon dried grapes (raisins), figs, etc. ; and the white, 
brittle granules found in the interior of these fruits, is grape sugar ; — hence 
the origin of the name. 

Grape sugar may be abundantly obtained from the juice of ripe grapes and 
pure honey, by washing with cold alcohol, which dissolves the fluid syrup. 
It may also be prepared by treating starcji-with sulphuric acid in the manner 
already described • sugar from this source has received the distinctive name 
of glucose, and is very largely employed in Europe for ordinary sweetening 
purposes'," for confectionary, for adulterating cane sugar, and for the manufac- 
ture of spirituous liquors by fermenting and distilling. In the United States, 
the low price of cane sugar renders its manufacture unprofitable. 

In addition to starch, woody fiber of all kinds, paper, cotton, flax, cotton and 
linen rags, and even saw-dust, may be converted into grape sugar by heating 
in connection with dilute sulphuric acid. The operation is somewhat slower 
than when starch alone is employed, which is partially explained by the fact, 
that the acid first changes the woody fiber into starch, and then the starch 
into dextrine and sugar. 

Almost all the acids, even when very dilute, convert cane sugar into grape 
sugar. 

Grape sugar is sometimes produced in the animal system, and its appear- 
ance in the urine in great quantities is a characteristic feature of a very fatal 
disease termed diabetes. 

Questions. — What is said of the production of beet, date, and maple sugars? What is 
caramel ? What are grape sugars ? What are familiar examples of grape sugar ? How- 
may it he prepared? What other substances besides starch may yield grape sugar? 
What is the action of acids upon cane sugar ? Does grape sugar ever occur in the animal 
system ? 



420 



ORGANIC CHEMISTRY. 



TOO. Essential Differences of Cane and Grape Sugars. 

— Cane sugars are popularly distinguished from every other variety of sugars 
by their greater sweetness or sweetening power ; three parts being equivalent 
in this respect to five of grape sugar. Cane sugar dissolves more readily in 
water than grape sugar ; one pound of cold water dissolving three pounds of 
the former and but one of the latter. Cane sugar, when pure, remains dry 
and unchanged in the air, crystallizes readily, and when acted upon by sul- 
phuric acid, is blackened; grape sugar, on the contrary, absorbs moisture 
from the atmosphere, and becomes damp ; is not easily crystallized, and when 
digested in sulphuric acid, dissolves freely without blackening. 

As respects chemical composition, cane sugar differs from starch and woody 
fiber in simply containing an additional equivalent of the elements of water — ■ 
the formula of the latter being Ci 2 Hi Oi , while that of cane sugar is C12H11O11. 
Grape sugar contains relatively less carbon than either starch or cane sugar, 
its formula being C12II14O14. 

Grape sugar may be prepared artificially from various substances, but cane 
sugar can not be so obtained. 

These two varieties of sugar may be easily distinguished from each other 
by their reactions with oxyd of copper: thus, if we add to separate solutions 
of cane and grape sugars a few drops of sulphate of copper (blue vitriol), and 
afterward caustic potash in excess, we obtain deep-blue liquids, which ex* 
hibit very different characters when heated; the solution of cane sugar re^ 
tains its blue color, while that of grape sugar throws down a copious reddish 
precipitate of suboxyd of copper. 

Sugar often acts the part of an acid, and is capable of uniting with bases — 
potash, baryta, lime, etc. — to form salts called saccharates. Most of the sugars, 
when left in contact with certain nitrogenized substances, called yeasts or fer- 
ments, become decomposed, and pass into alcohol and carbonic acid. Grape 
sugar is especially susceptible of this change ; and cane sugar, before it under- 
goes fermentation, always passes into grape sugar. 

701. Manna Sugar s, Ce H7 Og , are distinguished from other sugars in 
three particulars : they do not contain hydrogen and oxygen united to carbon 
in the proportions which form water; they are inferior in sweetness to other 
sugars ; and they do not ferment under the influence of yeast. Manna sugars 
are somewhat extensively distributed in the vegetable organization, and exist 
most abundantly in manna, which is a dried juice of certain species of ash- 
trees growing in southern Europe. They are also found in the juices of the 
onion, asparagus, celery, mushrooms, and in several sea- weeds; and may be 
artificially prepared from ordinary sugar by a peculiar kind of fermentation. , 

702. Sugar of Milk . — Lactine, C^H^O^. — This peculiar substance is 
the sweet principle of milk. When the curd is separated in the making of 



Questions. — What are the essential differences of cane and gTape sugar? By what 
chemical test may the two be distinguished ? How does sugar comport itself as respects 
the bases ? What is a property of most sugars ? What are the characteristics of manna 
sugars ? What is said of their occurrence ? What is said of the sugar of milk ? 



•ALBUMEN. 421 

cheese, the sugar remains in the whey, and may be obtained, in the form of 
white prismatic crystals, by evaporating the whey to a small bulk, and allow- 
ing it to cool. It is much less soluble and less sweet than cane sugar, and in 
a solid state feels gritty between the teeth. It is principally manufactured in 
Switzerland, and is used extensively in homoeopathic medicine, as envelope 
for remedial substances. It has hitherto been detected in only one vegetable 
production — the acorn. 

703. The conversion of starch into gummy matter and sugar, and that of 
the latter into starch, is a very common result in the vegetable kingdom. 
Unripe fruit, as apples, pears, etc., contain an abundance of starch ; this may 
be proved by applying the tincture of iodine to a freshly-cut surface. "When 
the fruit is completely ripened, this reaction can not, however, be obtained ; 
the starch, therefore, has disappeared, and has been replaced by sugar, as is 
made evident by the sweet taste which the fruits have acquired.* 

SECTION II. 

ALBUMEN, CASEINE, GLUTEN. 

704. Associated with the non-azotized substances in all plants, is another 
class of compounds, equally important, but much less abundant, than the for- 
mer. These are the nitrogenized or albuminous compounds, the principal of 
which are known as Albumen, Caseine, and Gluten. 

•. 705. A 1 b u m e n is widely disseminated through vegetable structures, and 
also exists abundantly in the animal economy ; the white of eggs, and the 
serum, or thin, transparent part of the blood, being essentially composed of 
albumen dissolved in water. 

Albumen dissolves freely in cold water, and forms a tasteless, glairy, trans- 
parent fluid ; if heated, however, to about 15.8° F., it coagulates, or becomes 
insoluble in either hot or cold water. This change may be especially noticed 
in the cooking of eggs. Alcohol, creasote, corrosive sublimate, and many 
other substances, are also capable of transforming albumen from a soluble into 
an insoluble condition. 

* " A similar metamorphosis is also noticed in the potato. The quantity of starch con' 
tained in 100 lbs. of the same kind of potatoes has been found to be in August, 10 pounds; 
in September, 14; in October, 15; in November, 16 ; in December, 17 ; in January, 17 ; 
in February, 16 ; in March, 15 ; in April, 13 ; in May, 10. Accordingly, the quantity of 
starch in potatoes increases during the autumn, remains stationary during the winter, and 
in the spring, after the germinating principle is excited, it diminishes. It is a well-known 
fact, that in germination, potatoes become soft, mucilaginous, and afterward sweet ; the 
dextrine formed from the starch rendering them mucilaginous, and the sugar formed 
from the dextrine rendering them sweet. The process of transformation advances still 
further in the earth ; the potatoes becoming softer and more watery, and when the starch 
is completely consumed in the growth of the young plant, the process of decay com- 
mences." — Stockh AEDT. 

Questions. — What fact illustrates the conversion of starch into sugar in nature ? What 
are the principal nitrogenized compounds of plants ? What is said of albumen ? What 
are its characteristic properties? Why do eggs harden in boiling? 



422 ORGANIC CHEMISTRY. 

When water containing a small portion of albumen is heated, the albumen 
is coagulated, and rises as a scum to the surface, carrying with it any small 
particles of impurity mechanically suspended in the liquid. It is in this way 
used for clarifying solutions of sugar and other liquids. 

Albumen is found in a soluble state in the sag of plants, in the humo rs of 
the eye, in the white of eggs, and in the serum of the blood; and in an in- 
soluble state in the seed s, leaves, and stalks of plants, and in the substance of 
which the brain and nerves of animals are composed. -*«- - 

706. C a s e i n e is a substance of both vegetable and animal origin, and is 
allied to albumen in its composition and properties. It differs from it, how- 
ever, in the circumstance that it is not coagulated by heat, although it readily 
experiences this change under the influence of acids. It is found abundantly 
in the seeds of leguminous plants; peas and beans containing from 20 to 25 
per cent, of their weight of it. It also exists in animal substances, especially 
in the curd of milk, which is known as animal caseine, and is the chief ingre- 
dient in cheese. Vegetable caseine, to distinguish it from animal caseine, is 
often called legumine, but the identity of the two" is well illustrated by the fact 
that the Chineselhake a real cheese from peas. Vegetable caseine may be 
obtained by macerating peas or beans in tepid water for several hours, and 
straining through a seive. The liquid which passes through contains caseine 
in solution, together with some starch, which separates by standing. From 
the supernatant liquor, which resembles skimmed milk in appearance, caseine 
may be precipitated by the addition of acetic acid, and when washed and 
dried, forms a brilliant, transparent mass. 

* 707. G 1 u t e n. — If flour be made into dough, and worked with the hand 
upon a seive, or piece of muslin, under a stream of water (Fig. 219), its starch 
gradually washes away, and there remains upon the seive a white, soft sticky 
substance, which has received the name of gluten. This substance exists in 
all the cereal grains, and constitutes about 10 per cent, of the weight of pure 
flour, and from 14 to 15 per cent, of the weight of bran. It is this principle 
which imparts to flour its plastic and adhesive properties. 

The lean part of the muscles of all animals, termed fibrme, resembles the 
gluten of plants so closely in composition and properties, that it may be re- 
garded as essentially the same substance, and hence gluten is very often 
called vegetable jibrine. 

708 Chemical Composition of Proteine. — Albumen and 
gluten are composed of carbon, hydrogen, oxygen, nitrogen, phosphorus, and 
sulphur; caseine contains the same elements, in nearly the same proportions, 
with the exception of phosphorus, which does not enter into its composition. 

According to the generally received opinion at the present day, all album- 

Questions — How is albumen employed for the clarifying of liquids ? What is said of 
caseine ? In what respect does it chiefly differ from albumen ? In what vegetable sub- 
stances does it especially occur ? In what animal substance ? By what other name is 
vegetable caseine known ? How may caceine be obtained ? What is gluten ? In what 
vegetable products is gluten especially found ? With what substance of animal origin 
does it correspond ? What is the chemical composition of albumen, caseine, and gluten ? 



ALBUMEN, CASEINE, GLUTEN. 



423 




inous matter (and by this term Fig. 219. 

We mean to include albumen, 
caseine, gluten, and all similar 
substances, originating either in 
vegetable or animal structures) 
are compounds of a peculiar and 
distinct principle, ca\\ed j^roteine. 
The composition of this organic 
radical is indicated by the for- 
mula C86H26N4O10, or by the 
symbol, Pr. Hence, albuminous 
substances, as a class, are very 
generally termed proteine com- 
pounds — the formula of albumen 
being lOPr-J-P+S ; of gluten, 
lOPr-f-P-f 2S; and of caseine, 
lOPrfS* 

By dissolving any albjirmjiojis 
substance in caustic, alkali, and 
adding acetic acid to the solution^prateine may be precipitated in the form 
of a grayish- white, inodorous solid, soluble in water and alcohol, and capable 
of uniting to form compounds with many acids and bases. 
\Jf09. Characteristics of the Albuminous Substances, 
——53.11 the albuminous substances, when subjected to heat, exhale an odor 
similar to that of burnt feathers, and leave, as an ultimate residue, a black, 
brilliant, spongy ooal. When perfectly dried, they are capable of indefinite 
preservation ; but when exposed to the joint influence of air and moisture, 
they are more susceptible of decomposition than any other class of organic 
substances — putrefying and calling into existence a multitude of microscopic 
animalculae. The decomposition of the albumen contained in wood, espe- 
cially in what is called the sap-wood, is regarded as the most active cause of 
its decay. Hence those substances like creosote, corrosive sublimate and the 
like, which form insoluble compounds with albuminous matter, existing either 
in animal or vegetable tissues, are the most effectual antiseptic agents ; the 
processes of kyanizing wood, and of smoking fish and meat, being familiar ex- 
amples of their action. The complete dessication of organic substances, or the 
extraction of their albuminous constituents by steeping in water, or steam, 
accomplish the same result. 



* It is proper to state, in this connection, that the theory which assumes the radical na- 
ture of proteine is very strenuously opposed by many chemists, and especially by Dumas, 
■who regards it as a product not pre-existing in albuminous compounds, but "as generated 
by the action of the alkalies on these bodies. 



Questions. — Of what radical are they supposed to be derivatives ? What are the char-** 
acteristics of proteine ? How is it obtained ? What are the general properties of the al- 
buminous substances ? 



424 ORGANIC CHEMISTRY. 

"When albuminous substances are dissolved in caustic alkali, the sulphur 
which they contain unites with the alkali to form a, soluble sulphuret, and 
the solution blackens paper moistened with sugar of lead. In this way the 
presence of sulphur in these compounds may be readily demonstrated. When 
an egg is boiled, the sulphur present in its albumen unites with a little free 
soda, which is also a constituent of the egg, to form sulphuret of sodium, 
and it is by the decomposition of this compound that the blackening of silver 
spoons used in contact with boiled eggs is occasioned. 

710. Nutritive Value of Vegetable Albuminous Con- 
stituents , — As the chief proximate constituents of animal structures, 
albumen, caseine, and fibrine have the same chemical composition as the al- 
buminous substances produced in the vegetable kingdom, the latter are re- 
garded as the special products provided by nature for the nutriment and 
support of animals ; or in other words, they are the vegetable principles out 
of which animal fibers and tissues are constructed. All experiments tend to 
confirm this conclusion, and prove that the value of a vegetable product as 
an article of food is very nearly in proportion to the quantity of albuminous 
or nitrogenous compounds which it contains. This subject will be further 
discussed hereafter. 



CHAPTER XVIII. 

NATURAL DECOMPOSITION OF ORGANIC COMPOUNDS. 

711. So long as organic bodies are pervaded by what is termed the vital 
principle, so long do they tend to maintain their form and properties essen- 
tially unchanged ; but when deprived of this influence, they obey the ordi- 
nary laws of chemical attraction, and readily undergo decomposition, the pro- 
ducts of such decomposition being mainly the result of a separation or falling 
apart of the complex substances which characterize the living structure, and 
a re-arrangement of their particles in simpler combinations. The nature of 
these changes, which vary greatly with the composition of the bodies con- 
cerned, and with the conditions to which they are subjected, may be gener- 
ally considered under three separate heads, viz., as decay, fermentation, and 
•putrefaction. 

712. Decay . — When vegetable tissue (wood, leaves, straw, etc.) is ex- 
posed to the action of atmospheric air and moisture, it absorbs oxygen and 



Questions. — How may the presence of sulphur in these bodies be demonstrated ? What 
is supposed to be their special office ? What is the proportionate value of a vegetable 
product as an article of food? What especially distinguishes living from dead organized 
matter ? What change does vegetable tissue undergo when exposed to air and moist- 
ure? 



DECOMPOSITION OF ORGANIC COMPOUNDS. 425 

undergoes a slow decay, which has been termed by Liebig eremacausis (slow 
combustion). The changes which take place in this process are very nearly 
the same as in the ordinary combustion of wood, except that they occur much 
more slowly. In both cases the constituents of the wood, by the addition 
of oxygen from the air, are converted into carbonic acid and water, and in 
both cases also the hydrogen is oxydized more rapidly than the carbon, as 
is shown by the darker color which wood assumes both in combustion and 
decay. Eremacausis further agrees with ordinary combustion, inasmuch as 
it can not take place without the access of air, and is uniformly attended with 
the evolution of heat, and sometimes with light — the total' amount of heat 
evolved being undoubtedly the same in both cases. (§ 469.) 

The brown or black matter into which vegetable tissue is converted by de- 
cay, has received the general name of humus, or vegetable mold, and is the 
substance which gives to fertile soils their rich black or brown appearance. 
Humus is not, however, regarded as a distinct compound, but rather as a 
mixture of several brown substances, which represent various degrees of de- 
composition of the original vegetable matter. These substances have received 
the names of humine, ulmine, humic acid, ulmic acid, geic acid, crenic and 
apocrenic acids. The two latter are soluble in water, and are mainly the 
cause of the deep yellow or brown colors which characterize the waters of 
bogs and swamps. The others are either entirely insoluble, or soluble only 
in alkaline solutions. The relation which these substances sustain to plants 
is an important one, and their presence in certain quantity in every soil is 
essential to its fertility. From the products of their decomposition— carbonic 
acid and water — plants derive, through their roots, from the soil, their chief 
supplies of nutriment. They also absorb and retain ammonia, another im- 
portant element of vegetable nutrition, and to some extent have undoubt- 
edly the power of producing it from the nitrogen of the atmosphere. The 
humus consumed in vegetation and removed from the soil in the substance 
of the crop, may be again restored to the land by plowing in straw and ani- 
mal manures, or green crops (clover, etc.), or by the alternation of plants 
which leave abundant roots in the soil (fallow plants), with such as have few 
roots (graius, etc.). 

Eremacausis is greatly promoted by heat and moisture, or the presence of 
the alkalies ; it is, on the contrary, arrested or retarded by cold and dryness. 
Wood, cordage, etc., exposed to the cold of the Arctic regions, or to the 
dry" atmosphere of Egypt will remain alike for years unaltered. 

713. Putrefaction , — The decomposition of vegetable tissue when air 
is wholly or partially excluded from it, as, for example, when buried in the 



Questions. — What is this change called ! What is the nature of the change ? What is 
the immediate product of the decay of vegetable tissue called ? What is the composition 
of humus? Whit produces the discoloration of the water of bogs and marshes? What 
relation do these substances sustain to vegetation ? How may humus consumed by vege- 
tation be restored to the soil ? What is the nature of the decomposition which takes place 
in vegetable tissue when air is excluded ? 



426 



ORGANIC CHEMISTRY 



ground, is essentially different from that of eremacausis. In this case the 
constituent elements rearrange themselves mutually into new products, either 
with or without the cooperation of the elements of water ; the oxygen gradu- 
ally uniting with the carbon to form carbonic acid, which separates and leaves 
as a residue substances rich in carbon and hydrogen — hydrocarbons. It is in 
this way that bituminous coal, peat, and brown-coal (lignite) have been formed 
from vegetable matter,* and also the natural gaseous carburets of hydrogen, 

viz., "marsh gas," obtained by 
Fig. 220. stirring the mud at the bottom 

of pools (see Fig. 220), and "fire- 
damp," evolved from rock-strata 
in mines. (§ 452.) Moist hay, 
leaves, manure, etc., when piled 
together in compact heaps undergo 
similar changes, and are converted 
into black, carbonaceous products. 
Decomposition of this character 
is termed putrefaction, and is 
somewhat analogous to the change 
which wood undergoes when sub- 
jected to dry distillation or incom- 
plete combustion. It differs from 
eremacausis (or decay), inasmuch as the latter can not take place without 
the free access of air, the oxygen of which is absorbed by the decaying bodies. 
The two methods of decomposition may, however, mutually replace each 
other, since all putrifying bodies pass into the state of decay when exposed 
freely to the air ; and all decaying matters into that of putrefaction when air 
is excluded. 

Nitrogenized animal and vegetable substances, on account of their complex 
constitution, undergo decay and putrefaction much more readily than non- 
azotized compounds, and the products of their decomposition are essentially 
different. Thus the oxygen of the substance unites with the carbon to form 




* Peat is mainly the product of the slow decay of certain species of marsh plants under 
water. Every peat-hog was undoubtedly, in the first instance, a marsh or swamp, which 
has been filled up and converted into a morass by the annual growth and decay of its sur- 
face vegetation. The quantity of vegetable meld which thus accumulates in the course 
of years is very great, and as the process of decomposition is slow and gradual, the aspect 
and constitution of the different successive layers of peat vary greatly — those near the sur- 
face consisting of the half decayed stems of mosses and of roots, while those of older 
formation scarcely exhibit any traces of their vegetable origin, and in some instances aro 
converted into a true bituminous coal. In many countries peat is extensively used as fuel, 
and furnishes by distillation oily products analogous to those obtained by the distillation 
of coal. 



Questions — What are the products of such decomposition ? Illustrate this. What Is 
decomposition of this character termed ? How does putrefaction differ from eremacau- 
sis ? What are the products of the putrefaction of nitrogenized substances ? 



DECOMPOSITION OF ORGANIC COMPOUNDS. 427 

carbonic acid, while the hydrogen divides itself between the nitrogen, the 
sulphur, and the phosphorus, and forms ammonia with sulphuretted and phos- 
phuretted hydrogen. It is to the presence of these last-named gaseous sub- 
stances that the very offensive odors given off during the putrefaction of azot- 
ized bodies are to be mainly ascribed. 

f 114. Fermentation. — When a nitrogenous substance undergoing 
putrefaction is brought in contact, under favorable "circumstances of tempera- 
ture and moisture, with a complex organic body of small stability, it is ca- 
pable of inducing in this latter substance, by the mere agency of its presence, 
a state of putrefaction or decomposition. In such cases the substance inducing 
decomposition is termed a "ferment" and the decomposition induced, "fer- 
mentation." For example, a solution of pure sugar may be preserved unal- 
teTe'd for any length of time, but if a minute quantity of putrescent matter 
containing nitrogen be added to it, fermentation at once takes place, and the 
elements of the sugar break up into alcohol and carbonic acid. " In the 
same manner, the most minute portion of milk, paste, juice of beet-root, flesh 
or blood, in the state of decomposition, causes fresh milk, paste, juice of beet- 
root; flesh or blood, to pass into the same condition when brought in contact 
with them." 

The method in which ferments act is not well understood, since they do 
not enter into combination with the fermenting substance or with any of its 
elements. The theory, however, most usually adopted is, that the molecules 
of the ferment, or substance already undergoing change, are capable of im- 
parting motion to the molecules of other substances by contact, and that 
through the impulse thus received, the equilibrium of forces previously exist- 
ing between the molecules of the body acted on are overcome and de- 
stroyed. 

' 115. Yeast . — The substance most potent in exciting fermentation in 
solutions of sugar is a species of microscopic vegetation which is spontaneously 
developed in the organs of plants, and in a large number of nitrogenous sub- 
stances, when left to putrify. This organism, which passes into a state of 
putrefactive decomposition with great readiness, is termed yeast, or ferment. 
It is obtained in the greatest abundance when a solution of sugar mixed with 
albuminous substances of animal or vegetable origin is exposed to the air 

I at ordinary temperatures. 

"When yeast is added to a solution of sugar, it not only excites fermentation, 
but if there are .albuminous substances present, it occasions the production 

. of an immense additional quantity of yeast. For example, if we add to clear 
fresh juice of ripe grapes a few particles of yeast, the liquid will in a short 
time grow thick and give off bubbles of gas, or ferment, and in a few hours 
a layer of grayish-yellow yeast will collect upon its surface. In the heat of 
the fermentation the yeast plants are produced in immense numbers, mil- 

Qtjestions. — Explain the meaning of ferment and fermentation. What are examples ? 
What is the theoretical action of ferments ? What is yeast ? How is it formed ? Illus- 
trate this. 



>^ 




428 ORGANIC CHEMISTRY. 

„ lions of its minute organisms being contained in 

the space of a single cubic inch. Fig. 221 repre- 
sents the appearance of the yeast globules under 
the microscope, and the manner in which they 
propagate by division. Ordinary brewer's yeast 
is formed in this manner in the fermentation of 
infusions of malt. Artificial yeast, or leaven, may 
b3 prepared by exposing a piece of dough for 
some days to a moderate temperature, until it 
© "^^^(^GX^o acquires a sour, or vinous odor. The fermenting 

agent in this case is the gluten of the dough in a 
state of incipient putrefaction. Yeast loses its 
power of exciting fermentation when perfectly 
dried, or heated to a temperature of 212° F., or if mixed with alcohol, acids, 
or alkalies, and finally by the completion of its own decomposition. 

716. Different Kinds of Fermentation. — The products of 
fermentation vary under different circumstances. The conversion of sacchar- 
ine liquids into alcohol and carbonic acid is termed vinous, or alcoholic fer- 
mentation. For the production of this change a temperature of from 50° to 
86° F. is necessary. Under 50° F. fermentation does not proceed. All 
vegetable bodies contain some substances which act as a ferment, and there- 
fore, by the addition of moisture and regulation of the temperature, various 
kinds of grain containing starch, and ripe fruits containing sugar, will un- 
dergo naturally the vinous fermentation. Thus cider is formed from apples, 
and beer from grain. 

A liquid which has already undergone the vinous or alcoholic fermentation, 
is capable of experiencing another change when exposed to the air in con- 
nection with a small quantity of decomposing azotized matter — its alcohol 
being converted into acetic acid and the liquid into vinegar. This has been 
called acetous fermentation. 

There are a variety of substances which, when added to fermentable 
liquids, even in very minute quantities, have the power of preventing de- 
composition ; such are, for example, the oil of mustard, sulphurous acid, ni- 
trous acid, etc. New cider, it is well known, is kept sweet by the addition 
of mustard-seed, or by burning sulphur in the barrels previous to filling with 
liquor. 

When azotized matters are beginning to decompose they are at first not 
able to excite the true alcoholic fermentation in solutions of sugar, but it is 
necessary for this that their decomposition should bo tolerably active and ad- 
vanced. But even in the early stage of their transformation they are able to 
effect a very important change in the elements of sugar, and cause it to un- 
dergo a peculiar kind of fermentation, the result of which is the production of 

Questions How may artificial yeast be prepared ? Under what circumstances does 

yeast lose its power? What is vinous fermentation? What are examples? What is 
acetous fermen'ation ? What substances are capable of arresting fermentation ? Is all 
decomposing azotized matter capable of inducing alcoholic fermentation ? Illustrate this. 



DECOMPOSITION OF ORGANIC COMPOUNDS. 429 

an acid called lactic acid, and a viscous substance analogous to sugar. This 
fermentation, which has been termed viscous, or lactic acid fermentation, is 
especially produced when milk or cheese curd is mixed with sugar at a tem- 
perature of 8G° to 94° F. If, however, the curd of milk is in an advanced 
stage of decomposition, it produces at the temperature of about 100° F. the 
vinous fermentation, and the sugar is converted into alcohol and carbonic 
acid. In this way the Tartars prepare a spirituous liquor from mare's milk, 
called " koumiss." 

TIT. Lactic acid derives its name from the circumstance that it is the acid 
which imparts sourness to milk, and is the immediate product of the decom- 
position of that liquid. Lactic acid, when kept in contact with caseine in tho 
first stage of its decomposition for some time, at a temperature of about 95° 
F., is itself capable of experiencing a transformation into a sour, pungent 
smelling liquid termed butyric acid, and the change in question is known 
as butyric fermentation. The conversion of starch into sugar by the action 
of diastase, is also regarded as a species of fermentation, and is termed 
" saccharine." Several other forms of fermentation in addition to those enu- 
merated, are also recognized, but the most important of them all are the al- 
coholic and acetous. 

118. Organic substances do not possess the power of entering sponta- 
neously into fermentation and putrefaction, but it is necessary that somo 
change in the attraction of their elements should previously take place. This 
exciting cause is undoubtedly the oxygen of the atmosphere which surrounds 
all bodies, and we accordingly find that eremacausis always precedes fermen- 
tation and putrefaction, and that it is not until after the absorption of a cer- 
tain quantity of oxygen that the signs of a transformation in the substances 
show themselves. When the condition of intestine motion is once excited, 
the presence of oxygen for the continuance of the action is no longer neces- 
sary. The smallest particle of an azotized substance in its act of decomposi- 
tion, also propagates this state of motion to the particles of the substance in 
contact with it, and although the air be afterward entirely excluded, fermen- 
tation or putrefaction will proceed uninterruptedly to its completion. Animal 
food of every kind, and even the most delicate vegetables, may be preserved 
unchanged for years, if heated to the temperature of boiling water in vessels 
from which the air is completely excluded. A fresh exposure to the air at 
any period will, however, induce fermentation.* — Liebig. 



* The method of putting up "preserved meats" is essentially as follows; the meat is 
first placed in a tin cylinder, which is then filled with a properly prepared soup, and a 
cover, pierced with a minute hole, is soldered on air- tight. The cylinder is next de- 
posited in a bath of chloride of calcium solution (which does not boil under a temperature 
of 320 J F.), where its contents are subjected to heat until sufficiently cooked. When this 
is effected, and the air in the interior completely expelled by the evolution of steam, tho 
minute orifice in the cover is suddenly and effectually closed with a drop of solder. The 

Questions — What is the acid of sour milk ? What is butyric fermentation ? Are there 
any other kinds of fermentation ? Do organic substances possess the power of sponta- 
neous change ? What is necessary to effect this ? How may animal food be preserved ? 



430 ORGANIC CHEMISTRY. 

U9. Poisons, Contagions, Miasms .— " When a chemical agent 
or substance is brought in contact with matter endowed with life (as, for 
example, if it is introduced into the stomach or any other part of the animal 
organization), it tends to enter into combination with it, and effect decompos- 
ition. This tendency is opposed by the vital principle, and the result will 
depend upon the strength of their respective actions. If the chemical element 
is forced to yield to the superior power of the vital action, it is digested, and 
exercises no chemical influence upon the living organ ; when, however, it is 
able to effect a change in the operation of the vital principle, as in changing its 
direction, strength, or intensity, without destroying it, it is said to act medi- 
cinally ; but when it obtains an ascendancy over the vital force, and tends to 
destroy it, it acts as a poison. Food will act as a poison, that is, will pro- 
duce disease, when it is able to exercise a chemical action by virtue of its 
quantity ; or when either its condition or presence retards, prevents, or arrests 
the motion of any organ. A medicament administered in excessive' quantity 
may act as a poison, and a poison in small doses, as a medicament. Thus the 
quantity of a substance and its condition must, obviously, completely change 
its chemical influence in the system." 

Some inorganic poisons, such as arsenic, corrosive- sublimate, etc, exert a 
destructive action upon animal life, by forming with the component parts of 
the body compounds which are not susceptible of the changes which it is the 
office of the vital principle to produce. Other inorganic poisons, like cor- 
rosive acids, destroy at once the form and structure of the tissues with which 
they arc brought in contact. In both cases the organs fad to fulfill their 
offices, and disease or death ensues. " If the quantity of poison is so small 
that only small portions of the body, which are capable of being regenerated, 
have entered into combination with it, then eschars (scabs) are produced, 
and the compounds of the dead tissues with the poison are thrown off by 
the healthy parts."* 

cylinder is then allowed to cool, and form a condensation of its contained vapor, both its 
ends are pressed inward, and become concave. Thus hermetically sealed, it is exposed in 
a test chamber, for at least a month, to a temperature above what it is ever likely to 
encounter ; from 90° to 110° F. If the process has failed, putrefaction takes place, and 
gas is evolved, which will cause the ends of the case to bulge, so as to render them con- 
vex instead of concave. But the contents of those cases which stand the test will infalli- 
bly keep perfectly sweet and good in any climate, and for any number of years. If there 
be any taint about the meat when put up, it invariably ferments, and is detected in the 
proving process. 

* " The limit at which substances like arsenic, corrosive sublimate, etc., cease to act aa 
poisons, may be determined with great certainty ; for since their combination with or- 
ganic matters must be regulated by chemical laws, death will inevitably result when the 
organ in contact with the poison finds sufficient of it to unite with atom for atom, whilst 
if the poison is present in smaller quantity, a part cf the organ will retain its vital func- 

Questioxs. — When a chemical agent is brought in contact with living matter, what 
takes place ? When will chemical substances act as food, as medicine, and as poison ? 
Illustrate how the quantity and condition of a substance may change its chemical influ- 
ence on the system ? How do inorganic poisons generally produce their destructive 
effects? 



DECOMPOSITION OF ORGANIC COMPOUNDS. 431 

"With respect to the action of poisons like Prussic acid, strychnia, etc., no 
very satisfactory explanation can be given. 

In addition to the poisons noticed, " there is a class of substances gener- 
ated during certain processes of decomposition, which act upon the animal 
economy as deadly poisons, not by entering into combination with it, or by 
reason of their containing a poisonous principle, but solely by virtue of their 
peculiar condition ;" in other words, these products being in a state of de- 
composition themselves, act as ferments, and by their simple presence tend to 
excite decomposition or disease in the animal substances with which they are 
brought in contact. 

The most striking illustration of this principle is to be found in the case 
of the wounds which physicians sometimes accidentally inflict upon them- 
selves in the dissection of dead bodies. The knife, in such instances, intro- 
duces through the wound a minute portion of matter in the state of decom- 
position or putrefaction, which acts as a ferment, and causes the healthy blood 
in contact with it to pass into the same decomposed state as itself; the ac- 
tion once commenced, extends with great rapidity, and very often affects the 
whole body and produces death — injuries to the system of this character being 
almost beyond the control of medical treatment. The virus of the small-pox, 
plague, etc., appear to act in like manner, inasmuch as the most careful ex- 
amination fails to extract from them any poisonous principle. When brought 
in contact, however, either directly or indirectly, with the blood, they commu- 
nicate to it their own condition. 

Contagion and miasm, or miasmata, are generally included among poisons 
of this class. 

"We apply the term contagion to that subtile matter which proceeds from a 
diseased person, or body, and which communicates disease to another person 
or body. It is characterized by its ability to reproduce itself. Miasm, on the 
other hand, is the product of the decay or putrefaction of animal or vegetable 
substances, and causes disease without being itself reproduced. 

The nature of the substances which constitute contagion and miasm is not 
well understood ; according to some authorities, they are merely putrid mat- 
ters, and according to others, they are microscopical animals or plants, which 
like yeast, readily undergo decomposition.* 



tions." The comparative weight of an equivalent, or of an atom of any one of the highly 
complex substances which make up the animal organism, is, however, so exceedingly 
great, that a very small amount of poison is sufficient to completely satisfy the combin- 
ing affinities of a very large quantity of animal substance ; the proportion in the case of 
fibrine and arsenic being as 6361 parts of the former to 1 of the latter. 

* Very many curious observations have been made upon these topics. A forest inter- 
posed to the passage of a current of moist air charged with pestilential miasmata, some- 
times preserves all behind it from its effects, whereas the uncovered portion of a district is 
exposed to disease. The trees, in such cases, appear to filter the air, and to purify it by 

Questions. — What is known respecting the action of poisons, like Prussic acid, etc. ? 
What other class of poisons are mentioned ? Explain the manner of their action. What 
are included under this class ? What is contagion ? What is miasm ? 



432 ORGANIC CHEMISTRY. 

Mildew is a species of decomposition occasioned by the development and 
growth of a class of microscopic fungi ; (a fungus being a cellular, flowerlecs 
plant). The dark spots observed upon awnings, sails, etc., exposed to the 
weather, are familiar examples of its action. The most effectual agent in pre- 
venting mildew is chloride of zinc. 

Many of the poisons which act as ferments, and readily excite disease when 
brought in contact with the blood, such as the contagious matter of small- 
pox, fevers, etc., are wholly inoperative when introduced into the stomach. 
The explanation of this is, that they are alkaline or neutral in their properties, 
and are therefore destroyed or neutralized by the free acid which always ex- 
ists in the stomach. Poisons of a similar character, however, which have 
an acid reaction, appear, when placed under the same circumstances, to 
retain all their frightful properties. The products of the incipient putrefac- 
tion of meat and fish are particularly liable to act in this manner. In Ger- 
many, especially, the effects of a poison of this character, resulting from a 
peculiar kind of putrefaction occurring in sausages, and hence termed the 
" sausage poison," have been very carefully studied. The symptoms which 
precede death in cases of poisoning by putrefied sausages are very remark- 
able. " There is a lingering and gradual wasting of muscular fiber, a%d of 
all the constituents of the body similarly composed ; the patient becomes 
much emaciated, dries to a complete mummy, and finally dies." 

The flesh of animals killed when overdriven or exhausted, is also very 
liable to produce diseases which, in the rapidity of their action and deadly 
effect, resemble cholera ; the symptoms, however, do not generally manifest 
themselves until some little time has elapsed after the food has 1 een received 
into the stomach. The origin of the poison in the meat in th ie instances 
is explained as follows : all mental and physical effort is accompanied by and 



removing the miasmata. Trees also appear to prevent miasmata by absorbing it. The 
negroes of the South plant the sunflower near their cabins as a preventative against fever 
and ague. Facts also show that malaria does not prevail in the neighborhood of swamps 
surrounded with thick forests — the vicinity of the Dismal Swamp, for example, being 
healthy, while the marshes of the adjacent sea-board are most pestilential." Flint, in his 
account of the Mississippi Valley, mentions the fact that the wood-cutters on the banks 
of the streams where the trees had been cut away, were constantly attacked by malarious 
fevers, while such diseases among the workmen in the forest were comparatively rare, 
although the ground on which they worked was quite as moist. Every tree which they 
left to decay on the ground helped to create the poison, while every tree left standing 
helped to absorb it. Many cases might be cited where the cutting down of woods has had 
a most unfavorable effect upon the health of the surrounding region. The district around 
Rome is only a celebrated instance of what is a very common experience. Dampness is 
not a source of miasmata, but decomposition caused by too rapid drying, whether of vege- 
table matter or animal infusoria. A ditch which alternates from wet to dry, or a pool 
which is weekly emptied and replenished as wind and shower follow each other, gives 
forth a much more deadly poison than ground which is uniformly and steadily satu- 
rated." 

Questions.— "What is mildew ? What are characteristic differences of action in poisons 
acting like ferments ? What are illustrations? What is the character of the flesh oi 
overdriven animals ? 



ALCOHOL AND ITS DERIVATIVES. 433 

requires an expenditure of healthy animal substance. The brain, for example, 
is undoubtedly used up by thinking, the muscles by exercise, the nerves by 
excitation. In the healthy state of the system, the waste thus occasioned is 
at once restored, and the products of decomposition are removed by the or- 
gans of secretion, and thrown off from the body. If the functions of the 
organs of secretion are impeded, the products of decomposition accumulate 
in the system and occasion disease. In the case of overdriven animals, the 
products of decomposition consequent upon unusual and excessive physical 
exertion, remain in the body, because the organs of secretion have not had 
sufficient opportunity to discharge their office before the animals are slaugh- 
tered. The meat, therefore, is full of substances in just that state of decom- 
position which enables them to act most effectually as ferments, and their 
presence, therefore, renders the flesh of the most healthy animal unwhole- 
some. It should also be mentioned, that the most severe cases of poisoning 
of this character seem to occur when the putrefactive fermentation in the 
meat has only just commenced, and when its presence is hardly discernible 
by the senses. 

720. Every form of disease is occasioned by changes or transformations 
which take place in organs in a manner different from what occurs in ordi- 
nary healthy action. If these transformations are perfected in constituents 
of the body which are not essential to life, without other parts taking a share 
in the decomposition, the form of the disease is termed mild or benignant ; 
but when the changes affect the organs essential to life, the disease is termed 
malignant. — Liebig. 



CHAPTER XIX. 

ALCOHOL AND ITS DERIVATIVES. 

7 21. The term alcohol is applied by chemists to a series of compounds of 
a dissimilar but analogous composition, and similar properties. They all 
consist of carbon, hydrogen, and oxygen, are all liquid at ordinary tempera- 
tures, and are characterized by possessing a high degree of volatility and a 
pungent taste and smell. The most important of the alcohols are wine alco- 
hol, C 4 H 6 2 , methylic alcohol, C2H4O2, and amylic alcohol, Ci Hi 2 O 2 . The 
term alcohol, however, in its ordinary acceptation, refers solely to the spirit- 
uous principle resulting from the fermentation of saccharine bodies. 

Sugar is the only substance susceptible of vinous fermentation, and the 
only substance from which alcohol can be derived. Potatoes, the cereal 

Questions. — Why is it liable to induce disease ? "What is the occasion of all disease ? 
"When is disease said to be benignant and when malignant? "What is the chemical signi- 
fication of the term alcohol ? What is its ordinary meaning ? From what substances 
only can alcohol be produced? How do we produce alcohol from bodies which consist 
mainly of starch ? 

19 



\ 



434 



ORGANIC CHEMISTRY. 



grains, and other vegetable products deficient in sugar from which alcohol is 
obtained, are rendered available for this purpose by first converting their 
starch into sugar. The various kinds of liquors prepared by means of fermen- 
t^on, may be conveniently divided into two classes — the beers, produced from 
the nutritive and starch containing grains and roots, and the wines produced 
from the juices of fruits which contain sugar. 

•722. T h e Beers . — When a solution of grape sugar is dissolved in 
water, and a little yeast added, fermentation speedily ensues, and the sugar 
breaks up into alcohol water,- and carbonic acid ; of these several bodies, the 
two former remain in the liquid, while the latter escapes as bubbles of gas 
into the air.* When cane sugar is used the results are the same, the yeast, 
however, in the first instance effecting a transformation of the cane sugar into 
grape sugar. For the completion of these changes it is not necessary that air 
should be present. 

When the cereal grains, etc., are used for the manufacture of alcohol, the 
first step, as has been already stated, consists in effecting a change of the 
starch into tliis sugar. This transformation may be brought about by the 
action of dilute sulphuric acid, but in practical operations this agent is rarely 
used, and the change is effected through the influence of diastase (§ 68S). 
In order to arrive at a clear understanding of this phenomenon, it is neces- 
sary to first consider the conditions under which diastase originates. 

A seed or grain consists essentially, in the first instance, of two substances, 
Fig. 222. starch and gluten, in which is contained a little rudi- 

mentary plantlet, called the germ or embryo. It is for 
the nourishment and support of this embryo, before it 
has attained sufficient development to be able to derive 
its own sustenance from the soil or air, -piG. 223. 
that the supplies of starch and gluten con- 
tained in the seed are provided. Fig. 222 
represents a grain of Indian corn, divided so as to show the em- 
bryo embedded in the starch and gluten, which make up the 
bulk of the seed. Fig. 223 represents, in like manner, a sec- 
tion of an acorn. Under the joint influence of heat and mois- 
ture, the embryo of the seed begins to sprout, or germinate, 





This decomposition may be represented as follows : — 

C H 

One atom of grape sugar = 1 2 14 

Two of alcohol = "8 12 

Four of carbonic acid = 4 

Two of water =0 2 
Total, 



12 14 14 
The yeast, which occasions the decomposition, takes no part in any of the combinations 

resulting. 



Question b.— When yeast is added to a solution of grape sugar, what takes place ? 
What in the case of cane sugar ? How is starch changed into sugar preliminary to the 
manufacture of alcohol ? Of what does a seed consist ? 



ALCOHOL AND ITS DERIVATIVES, 



435 



and puts forth a tiny stem or axis, bearing upon its summit a Fig. 224. 
pair of small leaves. It has now only to form a root by which 
to fix itself to the ground, to render it a perfect, though dim- 
inutive plant, capable of providing for itself. (Fig. 224 repre- 
sents a grain of Indian corn in the process of germination.) 
This root is and can only be formed from the starch and glu- 
ten contained in the seed; "but as both these substances are 
insoluble in water, they can not, in their natural state, pass on- 
wards from the body of the seed to supply the wants of the 
growing germ. It has been beautifully provided, therefore, that 
both of them should undergo chemical changes as the sprout- 
ing proceeds, and these changes take place at the base of the 
germ, exactly where and whon they are wanted for the forma- 
tion of the root." The gluten is accordingly first changed into 
diastase, and this acting upon the starch converts it wholly 
into grape sugar. 

Now the brewer, in the manufacture of spirituous liquors 
from grains, avails himself of this natural transformation in order 
to obtain the sugar, which alone is susceptible of vinous fer- 
mentation. The grain most usually selected for transformation 
is barley, which is first moistened in heaps, and spread upon the floor of a 
dark room to heat and sprout. When the germination has advanced to just 
the extent sufficient to convert the greater part of the starch into sugar, and 
the gluten into diastase, the action is arrested by heating the grain in a sort 
of kiln r which at once destroys the vitality of the germ. The necessity of 
thus violently arresting the progress of germination, grows out of the fact that 
the sugar" would be wholly consumed by its continuance and converted into . 
vegetable tissue. Barley thus treated is termed malt. 

The next step of the process consists in bruising the malt, and digesting it 
with water, gently warmed, in what is called the " mash-tub." The solution 
obtained contains sugar and diastase, and is termed wort. By standing a lit- 
tle time, the diastase acts upon any starch yet remaining in the seed, and con- 
verts it into sugar ; and it is also capable of changing, in a like manner, any 
unmalted grain or starch which may be added to the wort at this stage of the 
process. 

The change of all the starch into sugar being effected, the wort is next 
heated to boiling, which destroys any further action of the diastase. At this 
point, also, hops are introduced into the wort, which, besides imparting a pe- 
culiar bitterness and aroma to the liquid, help to clarify it. The boiled liquor, 
filtered and clarified, is next run off into shallow vessels, and cooled to a tem- 



Questions. — What takes place in germination? How does the brewer avail himself of 
the natural transformation of the starch and gluten of seeds ? "What is malt ? What is 
the first step of the process of brewing ? What is the second ? How is fermentation ef- 
fected? How is fermentation arrested ? Is the sugar contained in the wort allowed to 
entirely decompose. ? 



436 ORGANIC CHEMISTRY. 

perature of about 609 F. Yeast is then added, and fermentation allowed to 
proceed. "In a few hours bubbles of gas will be seen rising from all parts of 
the liquid, a ring of froth forming at first round its edge, and gradually in- 
creasing and spreading until it meets in the center, or until the whole surface 
becomes covered with a white, creamy foam of yeast. The bubbles of gas 
then rise and break in such numbers that they emit a low, hissing sound, 
while the yeast gradually continues to increase in thickness, and at last forms 
a tough, viscid crust, which the brewer skims off and removes as soon as he 
judges that the fermentation is complete, (the period of time varying from six 
to eight days)." 

In practice, the fermentation is always checked before the whole of the 
sugar is converted into alcohol, since, if perfect decomposition were effected, 
the beer would not keep, but would soon turn sour in the cask. The residue 
of undecomposed sugar also imparts a sweet, pleasant flavor to the beer. 

The liquor is next drawn off into casks, where it undergoes a second fermen- 
tation, far more slow and protracted, however, than the first ; this effects what 
is called a ripening of the beer, and is essential to its preservation. At the con- 
clusion of this second fermentation, the liquors must be kept tightly bunged, 
or corked up, since, as soon as the fermentation ceases, and air gets access to 
the liquor, oxydation commences, and induces acetous fermentation. The 
sparkle and foam of bottled liquors is owing to the carbonic acid gas which is 
generated in this second fermentation, and becomes dissolved in the liquors 
under pressure. 

The varieties of beer depend both upon the difference in their material and 
the different management in their production. The difference in the colors 
of ale and porter depends upon the color of the malt employed, which, in 
turn, is regulated by the length of time the malt is subjected to the heat in 
the kilns. 

723. Lager Beer. — Ordinary beers, even after the second fermenta- 
tion, contain a considerable quantity of albuminous or glutinous matter, 
which tends to decompose by contact with the air, and convert the alcohol 
mto acid (vinegar). Such liquors, therefore, are with difficulty preserved for 
a great length of time. In the preparation of lager L or Bavarian beer, the 
wort is fermented very slowly, and at an extremely low temperature, in large 
open vessels ; by which procedure the yeast produced, instead of rising at the 
top of the liquor, falls to the bottom, and a separation from the liquor of almost 
every trace of nitrogenized matters is at the same time effected. The fer- 
mentation thus carried on is very complete, and continues for weeks, or even 
months ; the liquor produced being as clear as champagne, and richly charged 
with carbonic acid. It may also be preserved for years without becoming 
sour. Lager beer derives its name from the long time it is allowed to lay 
{lager) in vats or casks, in cool cellars, previous to consumption. 



Questions. — Does any further fermentation take place ? "What occasions the 6parkle 
and foam of bottled liquors : What occasions the differences in beer ? What is " lagor" 
beer ? How is it produced ? What is the origin of its name ? 



ALCOHOL AND ITS DERIVATIVES. 437 

i(24. The intoxicating properties of malt liquors depend entirely upon the 
alcohol they contain. Of this, there is present in the stronger varieties of 
ales and beers (English ale, Albany ale, etc.), from 5f to 10 per cent, by 
weight; in porter and "brown stout," from 3£ to 6^- fin lager beer, from 2 
to 3-5 per cent. In addition to alcohol, the malt liquors all contain a certain 
quantitity of nutritive matters, consisting of undecomposed sugars, nitrogenized 
substances, oils, the aromatic parts of the hop, and certain mineral salts. In 
ordinary strong beers, the quantity of these substances varies from^to 8 per 
cent, of the entire weight ; in some of the German beers the per centage is 
much greater; so that beer is, to a considerable extent, food as well as 
drink. 

725. Wines . — The expressed juices of ripe fruits -containing sugar, con- 
tain also a peculiar azotized matter, which causes them to readily undergo fer- 
mentation without the addition of yeast. In ordinary summer weather, the 
clearest juice of the grape will enter into fermentation within a half an hour 
after its expression, and give off bubbles of gas. The azotized matter which 
occasions this fermentation will not, however, enter into ah active state of de- 
composition, unless free oxygen has access to ifc. " Consequently, whole 
grapes, or those in which the skins remain perfect and entire, may be dried 
and converted into raisins ; but if the skin is once injured, a little air gets in, 
and fermentation soon commences." 

The method of making wine is essentially as follows : the grapes are col- 
lected and pressed ; the juice, which is called must, is poured into vats, situ- 
ated in cellars, where, as the temperature is low, the fermentation proceeds so 
slowly, that it is not completed until after some months. During the fermen- 
tation, the impurities rise to the surface in the form of froth, or yeast, or set- 
tle to the bottom of the vats (lees), so that the pure wine is finally drawn off 
clear, and ready for use. "Wines intended to be sparkling or effervescing, are 
bottled before the fermentation is quite finished, so that the carbonic acid 
subsequently evolved remains stored up in the liquid. 

726. The popular qualities by which wines are known, are their strength, 
sweetness, acidity, and flavor. 

The strength of wine depends upon the alcohol it contains, the percentage 
of which varies greatly in different wines. The weaker hocks and sour 
wines contain about 9 per cent. ; champagne from 5 to 15 ; claret from 9 to 
15 ; while the stronger madeiras, sherries, and ports, contain from 18 to 24 
per cent. The sweetness and fruity character of wines is due to a portion 
of grape sugar which has escaped the decomposing action of the fermentation. 
Of this, there is no sensible quantity present in clarets, Burgundies, hocks, 

Questions To what are the intoxicating properties of malt liquors due ? How much 

alcohol do they contain on an average ? What other substances beside alcohol are con- 
tained in malt liquors ? Is it necessary to add yeast to the expressed juice of ripe fruits 
to excite fermentation ? Why do not grapes ferment upon the vines ? How is wine manu- 
factured ? How are sparkling wines prepared ? Upon what does the strength of wina 
depend? State the proportion of alcohol in various wines. Upon what does the sweet, 
ness of wines depend ? 



438 ORGANIC CHEMISTRY. 

etc. Sherries contain from 9 to 12 grains of sugar in an ounce; ports from 
16 to 30 ; and the so-called sweet wines (Cyprus, Malmsey, etc.) from 60 to 
100 grains. Some wines, like champagne, are artificially sweetened. 

All wines, malt liquors, and ciders, contain before undergoing acetous fer- 
mentation a variable proportion of free acid, which imparts to them a more or 
less distinctly sour taste ; but in each liquor the characteristic acid is differ- 
ent. Thus, malt liquors contain acetic acid ; ciders and the liquors allied to 
it, lactic acid ; while the acidity of wines is due to tartaric acid. In all of 
them acetic acid is also present in greater or less quantity, as it is always 
produced when the fermentation of alcoholic liquors is allowed to proceed 
too far ; but lactic acid is not found in malt beer or grape wine in sensible 
quantity; nor is tartaric acid found in beer or cider. When the fermented 
juice of the grape is left at rest, the tartaric acid gradually separates from it, 
and in combination with potash deposits itself as a crust upon the sides of 
the cask or bottles (cream of tartar). Hence by long keeping good wines 
become less acid, and every year added to their age increases in proportion 
their marketable value. Of the common wines, sherry is the least acid, and 
the Rhine wines of Germany the most so. — Johnson. 

The agreeable vinous odor of wine is due to the presence of a fragrant 
ethereal substance called cenanthic ether. This body does not exist in the 
juice of the grape, but is produced during fermentation, and may be isolated 
in the form of a fetid, highly fluid compound of carbon, hydrogen, and 
oxygen. In addition, however, to this substance, all wines contain certain 
fragrant principles which impart to them a peculiar bouquet, or flavor, and 
render wine so different and so preferable to beer, or any artificial mixture 
of spirit, sugar and water. They exist in wine in very minute quantities, and 
their chemical composition is not well understood.* 

In addition to the substances mentioned, all wines contain small quantities 
of other vegetable acids, together with various coloring, oily, and albuminous 
compounds. 

72 1. Ardent Spirits . — When fermented liquors are subjected to a 
moderate heat, the alcohol which they contain, by reason of its greater vola- 
tility, separates from the water, and together with a little steam and some 
odoriferous substances, rises as vapor. "When this operation is conducted in 



* Some of these peculiar bouquets are only developed by age, a fact which the -wine 
fancier so well appreciates, that he will give many times the original price for a kept wine, 
and millions of gallons are retained as stock in Europe because of this property. In ad- 
dition, wines of peculiar localities contain special bouquets which the art of the chemist 
entirely fails to account for. Thus the celebrated wine of Johaunisberg (the most costly 
of all wines by reason of its flavor) is only produced upon one estate in Germany. Tha 
wines of the neighboring valleys, Avhen subjected to analysis, show the same quantities of 
acid, sugar, and alcohol, but they do not possess the same bouquet. 

Questions. — What are the sweetest Avines? What is said of the acidity of fermented 
liquors in general '? What is the acid principle of wine ? Why do wines acquire sweet- 
ness by age? To what is the vinous odor of wine due ? What is said of the bouquet of 
wines ? What are ardent spirits ? 



ALCOHOL AND ITS DERIVATIVES. 



439 




close vessels (retorts), and the evolved vapors are collected and condensed by 
cooling (see Fig. 225), liquors containing a large percentage of alcohol are 
obtained. To such products of distilla- 
tion only is the term ardent spirits prop- 
erly applied. 

Every different fermented liquor, when 
distilled, yields an ardent spirit which is 
characterized by a peculiar flavor, and is 
distinguished by a name of its own. 
Thus, brandy is the product obtained by 
the distillation of wine, and rum the pro- 
duct of distilling fermented molasses. 
Whiskey is manufactured from corn, rye, JJ 
or potatoes in the following manner : the 
grain or potatoes, boiled or mashed, are 
mixed with a portion of barley-malt and warm water to form a paste, which 
is allowed to stand for a tlmeatah elevated temperature. Under these con- 
ditions the diastase of the malt converts the starch into sugar, which is then 
fermented in the usual manner by the addition of yeast. When the fer- 
mentation is concluded, the mass is placed in a still, and the spirituous prin- 
ciple distilled over by heat. The condensed product is whiskey, while the 
residue left in the still, called slops, or swill, is used as food for hogs and 
cows.* Ginjs prepared by rectifying {redistilling) the spirit obtained from a 
mixture of fermented rye and barley with juniper berries. By this means it 
loses the crude flavor it originally had, and acquires the agreeable one of 
junipers. 

The percentage of absolute alcohol contained in ardent spirits intended for 
consumption (i. e., strong brandy, rum, whiskey, etc.) varies from 50 to 70 
per cent. When these are submitted to distillation, a stronger liquor, called 
spirits of wine, is obtained. The product of the redistillation of this last is 
called rectified spirits of wine, ox rectified alcohol, and contains about 90 per 
cent, of alcohol and the balance water. It is the strongest alcohol known in 
commerce. The quantity of water remaining in rectified spirits of wine can 
not be separated by simple distillation, but is accomplished by mixing the 
spirits of wine with chloride of calcium, or some other substance which has 
so strong an affinity for water that it absorbs it, and allows the alcohol to 
distil over pure. In this^ condition the alcohol is termed absolute, or anhy- 
drous. Proof spirit is a mixture of equal parts of water and alcohol. 



* The milk yielded by cows fed on this refuse is considered unhealthy, and is popularly 
called " swill milk." 



Questions.— Is the distillate of all fermented liquors the same? What is brandy? 
What is rum? How and from what is whiskey manufactured ? What is gin ? What is 
the percentage of alcohol in ardent spirits ? What are spirits of wine ? What is rectified 
alcohol? What is pure alcohol called ? How is it prepared? What is proof spirit ? 



440 



ORGANIC CHEMISTRY. 



It was formerly the custom to estimate the strength of an alcoholic liquor 
by igniting a little of it in connection with gunpowder ; if the powder was 
fired, the spirit was considered strong, and called proof; if, on the contrary, 
it contained more than half water, the powder was not ignited, and the spirit 
was said to be below proof. The quantity of alcohol contained in a solution 
is now, however, calculated by determining its specific gravity (§ 40), or 
Tig 226 more conveniently by means of the alcoholometer (see 

Fig. 226), which is so weighted and graduated that it 
sinks to the topmost point of the scale A, which is 
marked 100°, in absolute alcohol, and to the lowest 
degree in pure water, which is marked 1° — interme- 
diate positions indicating proportional mixtures of the 
two liquids. 

728. Properties of Alcohol — Pure, or 
strong alcohol, is a highly volatile, mobile liquid, about 
one fifth lighter than water (sp. g. 0*195) possessing 
an agreeable, penetrating odor, and a hot, burning 
taste. It is very combustible, and burns with a pale 
blue flame without smoke, but with intense heat. It 
has a strong affinity for water, and absorbs or extracts 
it from substances with which it is brought in contact. 
On this account, taken in connection with its property 
of coagulating or hardening albumen, it acts as a pow- 
erful antiseptic, and is much used to preserve organic substances from putre- 
faction. Strong alcohol has never been frozen.* "When taken into the 
stomach it acts as a deadly poison, but when largely diluted with water it is, 
as is well known, stimulating and intoxicating. The solvent powers of alco- 
hol are very great ; it dissolves a great number of organic substances which 
are insoluble in water, such as the volatile oils and the resins, together with 
many acids, salts, the caustic alkalies, and other substances. Alcoholic ex- 
tracts of medicinal plants, roots, barks, etc., constitute the tinctures of phar- 
macy, and most of the liquid perfumes (eau de Cologne, etc.) are solutions of 
fragrant and volatile oils in alcohol. Many varnishes, also, are formed by 
dissolving resins in alcohol. 

129. Bread . — The preparation of bread is properly considered in con- 
nection with the subject of vinous fermentation: — 

The flour of wheat and other grains which enter into the composition of 
bread, consists mainly of starch, gluten, and water, together with small pro- 




* M. Despretz of Paris, in 1840, succeeded, by the rapid evaporation of liquid protoxyd 
of nitrogen and solidified carbonic acid, in producing a degree of cold sufficient to deprive 
alcohol in part of its transparency, and render it thick and viscid. 



Questions. — How is the quantity of alcohol in a liquor determined ? What are the 
properties of alcohol ? What is said of its solvent powers? What are tinctures ? How 
are liquid perfumes generally prepared ? What is the composition of flour ? 



ALCOHOL AND ITS DERIVATIVES. .441 

portions of sugar and gum.* The first step in the process of bread-making, is 
to mix together, in a suitable vessel, a proper proportion of flour, yeast, warm 
water, and common salt. This mixture, which is called the sponge, is worked 
up to the consistence of stiff batter, and then left for a few hours in a warm 
atmosphere, during which time the yeast excites fermentation in the sugar, 
and occasions its conversion into alcohol and carbonic acid. The gas thus 
generated does not escape in bubbles, but is retained by the tenacious and 
viscid dough, which, in consequence, becomes light and porous, and swells up 
to about twice its original size. 

"When the fermentation has proceeded sufficiently far, about twice as much 
flour as was originally taken is added to the sponge, and the two are care- 
fully kneaded together. This is a very laborious part of the operation, but is 
quite essential to the success of the process, since, if it is not very thoroughly 
attended to, the half-fermented sponge will not be equally and uniformly dis- 
tributed throughout the whole of the dough. 

If the dough be now put into a hot oven, the fermentation is at first increased 
and the size and porosity of the loaf are also greatly augmented by the ex- 
pansion of the carbonic acid gas contained in its cellular spaces. "When, 
however, the whole has been heated to nearly tho temperature of boiling 
water, the fermentation is suddenly arrested ; and the alcohol and a largo 
proportion of the water employed in mixing the dough, being at the same 
time volatilized by the heat, the cellular portions of the baked bread ac- 







* Flint-wheat contains, on an average, about 56 parts of starch, 14 of gluten, S of sugar, 
5 of gum, 2 of bran, and from 10 to 13 parts of water. The manner in which the bran, the 
gluten, and the starch are respectively distributed FlQ 227. 

throughout the cereal grains, is shown by the fol- 

lowing section of a fully-ripe grain of rye, highly ^-^^coooooc^ 
magnified. (See Fig. 2C~.) a represents the outer- -^==ir S?J;T^Ti> f^T ^i =f% j _ T) 
Beed coat, consisting of three rows of thick-walled fiM|F 
cells ; 6, the inner seed coat, composed of a single layer 
of thick-walled cells, having scarcely any cavity ; c, 
a layer of cells containing gluten. These three to- 
gether form the bran, d represents the cells con- 
taining starch grains in the interior of the seed. 
The outer coating of the seed contains only 3 or 4 
per cent, of gluten, while the inner coating contains from 14 to 20 per cent. All this i3 
separated in the bran. In addition to this, however, gluten is diffused everywhere through- 
out the mass of grain, among the cells containing starch. As the nutritive quality of any 
variety of grain depends very much upon the proportion of gluten which it contains, and 
as the bran embodies a larger proportion of this substance than the white part of the flour, 
it is obvious, that by sifting out the bran, as is usually done, we render the flour less nu- 
tritious. The bran generally constitutes about one fourth part of the whole weight of the 
grain. When wheat is burned, there is left about 2 per cent, ash, nearly one half of which 
consists of phosphoric acid: the other constituents being mainly potash, silica, magnesia, 
soda, oxyd of iron, etc. These mineral ingredients are unequally diffused throughout 
the seed : fine flour containing the smallest proportion, and the bran the most. 

Questions.— What is the first step in the process of bread-making? What is the ne' 
cessity of producing fermentation in dough of bread? What is the second stage of the 
process ? What occurs in the baking ? 

19* 






442 . ORGANIC CHEMISTRY. 

quire so much solidity, that they retain their form and structure permanently. 
If, however, the heat of the oven is not properly regulated, or if the dough 
contains too much water, the cellular portions harden too slowly, and on tho 
escape of the carbonic acid, collapse and run together {slack-baking). The 
alcohol which escapes from the bread in baking may, by means of a proper 
apparatus, be collected and condensed into spirits, and this, in fact, is done in 
some of the European bakeries. 

The yeast, in converting the sugar of the flour into alcohol and carbonic 
acid, acts also upon the starch, in the manner of diastase, and transforms a 
portion of it into sugar ; so that, although the sugar, which originally existed 
in the flour, is almost completely decomposed, the amount present in the 
bread remains very nearly constant. " It is sometimes stated, that, by tho 
ordinary mode of bread-making, a large portion of the most valuable part of 
flour is destroyed by fermentation. This, however, is not the case. Very 
little of the azotized matter of the flour is lost during the fermentation of the 
dough : the chief effect produced is a loss of a portion of the sugar ; but as 
nearly an equal quantity i3 formed from the starch, the real effect of the fer- 
mentation may be said to be principally the loss of about 5 per cent, of starch."' 
— Solly. 

. The addition of common salt to bread renders it more wholesome and di- 
gestible, and also assists in its preservation. 

The quantity of water in well-baked wheaten bread amounts to about 45 
per cent., or, in other words, the bread we eat is about one half water. 
Bread that has been kept for a few days, loses the characteristic softness 
which distinguishes it when fresh-baken, and becomes "crumbly," and ap- 
parently drier. In this condition it is known as stale tread. The change, 
however, is not due to any lo s of water, but to a change in the internal ar- 
rangement of the molecules of the bread. 

The solubility of bread, and its consequent ready digestibility, is somewhat 
mcreased by toasting, the starch being thereby converted into a modified 
gum (§ 689). 

730. As the process of fermenting bread, in order to -render it light and 
porous, is troublesome, and somewhat uncertain, various attempts have been 
made to effect the same object by other agencies. The best of the substi- 
Btituted methods is undoubtedly that in which bi-carbonate of soda and hy- 
drochloric (muriatic) acid are employed. A small, but definite quantity of 
carbonate of soda is first thoroughly mixed with the flour, and enough pure 
acid to perfectly neutralize it is then added to the proper quantity of water. 
The flour and the acid water being then thoroughly incorporated, the acid 
acts upon the carbonate of soda, decomposes it, expels its carbonic acid, and 

Questions. — When is bread said to be slacked baked? Can the alcohol evolved in 
bread-baking be collected? What action does the yeast exert on the starch of the flour? 
"What is the general effect of fermentation on the constituents of the bread ? What effect 
has common salt on bread ? What percentage of water does bread contain ? What is 
Btale bread? What occasions this change? What effect does toasting have upon bread? 
Is there any way of rendering bread light and porous without fermentation ? 






ALCOHOL AND ITS DERIVATIVES. 443 

unites with the soda to form common salt. The result is the production of a 
light, spongy dough, as in ordinary fermentation, while the salt formed and 
remaining in the dough, renders the addition of this substance, in the first in- 
stance, unnecessary. The most serious objection to this plan is the difficulty 
of procuring pure hydrochloric acid, and of regulating the proportions of acid and 
soda. Tartaric acid may be substituted in the place of hydrochloric acid, and 
the so-called yeast powders are generally prepared by mixing bi-carbonate of 
soda and tartaric acid in proper proportions. The carbonate of ammonia is 
also not unfrequently used (§ 525). 

731. Sources of Alcohol . — Alcohol is not a principle existing in 
nature, elaborated and stored up by the plants ; but is always a product of 
the destructive decomposition of highly-organized matter. The principal 
sources from which crude alcohol is obtained, are the most valuable of our 
cereal grains, immense quantities of which are annually used for this purpose, 
and of course to the same extent the aggregate supply of food for man is di- 
minished. The waste of raw material which accompanies the manufacture 
of alcohol from grain is also very great, since the nitrogenized elements of the 
grain do not enter into its composition, and are accordingly lost for any useful 
purpose ; while the starchy and saccharine constituents are converted to the 
extent of half their weight into valueless carbonic acid and water. Woody 
fiber, it will be remembered, has identically the same composition as starch, 
and, like it, may be converted by the action of acids into grape sugar, which is 
capable of furnishing alcohol. This process, however, by reason of its ex- 
pense, is not practically useful ; but its consideration has much of interest, 
since the discovery of a cheap and ready method of converting woody-fiber, 
and bodies of like composition and character, into glucose, to be used in the 
manufacture of alcohol, would prove one of the most valuable discoveries in 
the annals of science. 

'732. Products of the Action of Acids upon Alcohol. 

Ether . — "When equal weights of strong alcohol and oil of vitriol are - 
heated to ebullition in a retort, a colorless, highly volatile liquid distils over, 
which is known as ether, or sulphuric ether. As soon as the contents of the 
retort blacken and froth, the process must be discontinued, or otherwise the 
distillate will be contaminated by other substances. 

The formation of this liquid may be explained as follows : alcohol is as- 
sumed to be the hydrated oxyd of an organic radical ethyle, its composition 
being represented by the formula C4H602==C.iH 5 0-f-HO. "When sulphuric 
acid is added to alcohol and heated, it unites with the oxyd of ethyle to form 
a bi-sulphate (dUsO/iSC^), and from this compound at a higher temperature 
the oxyd of ethyle (ether) separates and distils over as a vapor. The alcohol, 
therefore, is converted into ether by the simple loss of an atom of water. 
The prefix sulphuric, as applied to ether, is merely intended to indicate its 

Questions. — "What are yeast powders ? What is said of the sources from which alcohol 
is manufactured, and of its production ? How is ether prepared ? "What is the theory 
of its production? Does sulphuric ether contain any sulphuric acid? 



444 ORGANIC CHEMISTRY. 

origin and distinguish it from other bodies of like character, since it contains 
no sulphuric acid in its composition. 

Ether is a colorless, transparent, fragrant liquid, exceedingly thin and mo- 
bile. It boils at 96° F. (or when exposed to the sun in summer), and may be 
frozen by exposure to severe cold. In the open air it evaporates with great 
rapidity, and occasions thereby a degree of cold sufficient even to freeze water 
(§ 1 64). This property may be illustrated by allowing a few drops of it to evapo- 
rate upon the hand. It is highly combustible, both in the state of liquid and 
vapor, and on this account should never be brought near a flame. With 
atmospheric air, or oxygen, its vapor forms explosive mixtures. This may 
be experimentally shown by pouring a few drops into a tumbler, and after 
a little time applying a burning taper. Ether mixes with alcohol in all pro- 
portions, but is very sparingly soluble in water. It dissolves most oily and 
fatty substances with great readiness, but its solvent powers generally are far 
more limited than those of alcohol. 

"When the vapor of ether, mixed with atmospheric air, is inhaled, it pro- 
duces at first a species of intoxication, which is speedily succeeded by a kind 
of stupor, during which the system is nearly insensible to pain. This impor- 
tant property is not, however, confined to ether alone, but is possessed by 
nearly all the gaseous hydrocarbons, and by some in a much greater de- 
gree. Ether, however, was the first substance employed as an ansesthetio 
agent, and under all circumstances must be regarded as the safest, no acci- 
dents from its moderate inhalation having ever been recorded. 

133. Varieties of Ether , — By distilling alcohol with various acids, 
different combinations of the radical ethyle may be produced, which are gen- 
erally spoken of as kinds of ethers. Thus, by distilling a mixture of alco- 
hol, sulphuric and acetic acids, we obtain an exceedingly fragrant, volatile 
liquid, acetate of the oxyd of ethyle, or acetic ether. The fragrant odor of 
this body may be evolved by slightly heating in a test tube a mixture of 
the above-named substances. In like manner, with the aid of nitric acid we 
may obtain a nitrous ether, which is much used in medicine under the name 
of sweet spirits of niter ; and with butyric acid, a butyric ether, which has the 
odor of rum, and is now prepared for the purpose of imparting to alcohol 
this flavor in the fabrication of liquors. 

• 734. Products of the Oxydation of Alcohol. — When al- 
cohol or ether are burned in free air, the products of combustion, as with all 
similar hydrocarbons, are carbonic acid and water. Under certain circum- 
stances, however, these substances undergo a partial oxydation, in which the 
hydrogen alone is oxydated or separated, leaving the carbon unaffected. 
The result is the formation of a series of compounds which are supposed to 
contain a new organic radical called acetyle, .C4H3, derived from ethyle, 
C4H5, by the removal of 2 equivalents of hydrogen by oxydation. 

Questions. — What are the properties of ether ? What is said of its solvent powers ? 
What of its anaesthetic properties? Is this property confined to ether? How may dif- 
ferent varieties of ether be prepared ? Illustrate this by examples. What is the product 
of the ordinary combustion of alcohol ? What is acetyle ? How is it formed ? 







ALCOHOL AND ITS DERIVATIVES. 445 

735. Aldehyde . — The first known product of this series is a hydrate 
of the oxyd of acetyle, CVHsO-f-HO, called aldehyde (from al, alcohol, de, from 
which, hyd, hydrogen, is taken). It is a limpid, colorless liquid, possessing a 
peculiarly suffocating odor, and may be prepared by distilling a mixture of 
alcohol, oil of vitriol, and the peroxyd of manganese. It may 
also be easily produced, and its characteristic odor illustrated, 
by plunging a coil of fine platinum wire heated to redness into a 
vessel containing a mixture of alcohol or ether vapor, and at- 
mospheric air. (See Fig. 228, also § 469.) The aldehyde is 
formed in this experiment because the oxydation is not sufficient 
to occasion a complete combustion of the alcohol vapor. Alde- 
hyde dissolves sulphur, phosphorus, and iodine, and is especially 
remarkable for its affinity for oxygen, in consequence of which 
it is capable of reducing many of the metallic salts. The addi- 
tion of a little aldehyde in water to an ammoniacal solution of 
nitrate of silver, occasions the immediate precipitation of the silver as a bril- 
liant white metal. 

136. Acetic Acid is well known as the acid of vinegar, which latter 
substance is, in fact, a very dilute acetic acid, containing also much saccharine 
and mucilaginous matter. Acetic acid is regarded as a hydrated teroxyd of 
the same radical, acetyle, which enters into the composition of aldehyde — its 
composition being represented by the formula C 4 H 3 03-{-HO. 

Alcohol, when pure, or merely mixed with water, undergoes no change 
when exposed to the air ; but the presence or contact of various foreign sub- 
stances, dispose it to absorb oxygen. Thus, if a few drops of strong spirits of 
wine be let fall upon a little platinum black, the oxygen condensed in the 
pores of the latter unites so rapidly with the alcohol, as to occasion its instant 
inflammation. Under the same circumstances, when the spirit is mixed with 
a little water, oxydation still takes place, but with less energy, and the alco- 
hol is converted into acetic acid. In these transformations the platinum 
itself experiences no change. The oxydation of alcohol, through the agency 
of platinum black, may be experimentally exhibited, also, by placing a capsule 
containing platinum black upon a plate by the side of a small vessel of alco- 
hol, and exposing the whole, covered with a bell-glass, to the sunshine. 
In a short time, the vapor of acetic acid will be observed to condense on the 
sides of the jar, and run down in drops ; and by occasionally admitting fresh 
air, the whole of the alcohol may in a few hours be acidified. 

The oxydation of alcohol, at the expense of the oxygen of the air, is also 
effected by the presence of almost any azotized matter (ferment) susceptible 
of putrefaction. Cider, wine, and beer naturally contain such substances, and 



Qitestions. — What is aldehyde ? "What are its properties ? How is it formed ? What 
is the acid contained in vinegar? What is its chemical composition? Under what cir- 
cumstances is alcohol oxydated ? How may the transformation of alcohol into acetic acid 
be illustrated? What is the action of ferments on alcohol? Why do cider, beer, etc.» 
turn sour by exposure to the air ? 



446 



ORGANIC CHEMISTRY. 






therefore readily undergo acetous fermentation when exposed to the air, at a 
moderate temperature, and become converted into vinegar (acetic acid). 
During this fermentation of alcoholic liquors, a mucilaginous substance, con- 
sisting chiefly of albuminous matter, is separated, which, from its influence in 
exciting or promoting acetous fermentation, is popularly termed the mother of 
vinegar. Acidification of this character occurs most readily immediately after 
a spirituous fermentation which has taken place at too high a temperature ; 
hence brewers, during the summer months, experience much trouble in pre- 
venting their fermenting wort and mash from turning sour. 

737. Yinegar is now manufactured, on a large scale, directly from alcohol, 
by diluting it with water, adding a little yeast, and exposing the mixture to 
the air. This last is best effected by causing the liquor to trickle slowly 

through a cask filled with shavings of beech- 
wood, and arranged as is represented in Fig. 
229. The head of the cask, d, is closed with 
a shelf, c, perforated with many small holes, 
through which threads are passed to conduct 
the liquor downward, and distribute it evenly 
over the interior. The shavings, first soaked 
in vinegar, are placed loosely in the cask, 
a free circulation of air between them being 
provided for by means of holes, a, in the 
sides of the cask. In this way the alco- 
holic liquor is caused to present an immense 
extended surface to the action of the air, and 
oxydation takes place so rapidly, that very 
frequently, by the time the liquid has trickled 
to the bottom of the cask, it no longer con- 
tains any alcohol, but is entirely converted into vinegar. Usually, however, it 
is necessary to pass the liquid through the apparatus a number of times before 
this change can be completely effected. The presence of acetic acid itself 
assists the action of acidification, and it is for this reason that the shavings 
are soaked in vinegar before using. This process is known as the quick 
method of making vinegar. 

The pyroligneous acid (or wood vinegar), obtained by the distillation of 
hard-wood in close vessels (§ 680), is an impure acetic acid, and as such is 
1 irgely used in dyeing and calico-printing ; the presence, however, of certain 
empyreumatic substances extracted from the wood, impart to it a disagreeable, 
smoky odor, and render it unfit for purposes of domestic economy. 

The acid liquids obtained by the above-mentioned processes, are not pure 
acetic acid, but merely solutions of it in water. This may be concentrated, but 




Questions. — What is the mother of vinegar? Under what circumstances does acidifi- 
cation occur most readily ? Describe the quick process of making vinegar ? What other 
product is a source of acetic acid ? Is the acid liquid obtained by the oxydation of alcohol 
pure acetic acid ? 



ALCOHOL AND ITS DERIVATIVES. 447 

if we attempt to obtain the acid free from any water by distillation, it is de- 
composed. Acetic acid in a separate state is prepared by neutralizing vinegar 
with soda or lime, evaporating to dryness, and distilling the solid residue in 
connection with sulphuric acid. The evolved vapors condensed, furnish a 
colorless, intensely-sour liquid, which possesses a pungent, fragrant odor, and 
blisters the skin. It mixes with water in all proportions, forming vinegars of 
different degrees of strength. Common table vinegar usually contains from 
3 to 5 per cent, of acetic acid. The salts of vinegar, sold by druggists as a 
reviving scenf in sickness and fainting, consist of sulphate of potash, impreg- 
nated with acetic acid. Acetic acid dissolves many organic bodies, such as 
gluten, gelatine, gum, resins, the white of eggs, etc. ; hence, its use as vine- 
gar, in moderation, promotes digestion. When vinegar i.s exposed to cold, the 
water contained in it is frozen before the acetic acid is ; hence, weak vinegar 

\ is made stronger by partial freezing. 

\Y * 738. Salts of Acetic Acid . — Acetic acid unites with most bases to 

V form an important class of salts called acetates, all of which are soluble in 

I water. Acetate of lead, PbO, C4H3O3, the sugar of lead of commerce, is a white 

v,\ salt formed by dissolving oxyd of lead (litharge) in acetic acid. It possesses 

|vA a very sweet astringent taste, and is often employed in medicine, but when 
taken internally in any other than minute quantities is a poison. Acetate of 
<k copper constitutes verdigris (§ G13). Acetates of alumina and of iron are 
^> salts much used in dyeing and calico printing. 

139. Methylic Alcohol . — In connection with the pyroligneous acid 
obtained by the distillation of wood in close vessels, there also passes over a 
volatile inflammable liquid, which is allied to alcohol in its composition and 
properties. This substance in its pure state is known as methylic alcohol, or 
wood-spirit, and is supposed to be the hydrated oxyd of a radical called 
wnethyle, the constitution of which is represented by the formula C2H3, and 
that of its alcohol by C2H3O+HO. Crude pyroligneous acid contains about 
l-100th of its weight of this substance, which is separated from it by distil- 
lation. It occurs as an article of commerce, and is often substituted for al- 
cohol in various processes in the arts. Its odor, however, is quite different 
from that of ordinary alcohol. 

740. Formic Acid , — As alcohol by oxydation, under the influence 
of finely divided platinum, gives rise to acetic acid, so wood-spirit, under 
similar circumstances, produces an acid product which has been called formic, 
from the circumstance, that a similar acid may be extracted from ants by 
distilling them with water. As acetic acid is regarded as the hydrated ter- 
oxyd of the radical acetyle, so formic acid is considered as the hydrated ter- 
oxyd of a new radical formyle, which is derived from methyle as acetyle is 
from ethyle — the formula of formyle being C2II, and that of formic acid, 

Questions.— How is acetic acid prepared? What are the properties of acetic acid? 
What are salts of vinegar ? What is said of vinegar ? What are acetates ? What is sugar 
of lead ? What are other important acetates ? What is said of methylic alcohol ? 
is its chemical constitution ? What is formic acid ? What is its composition ? 









448 ORGANIC CHEMISTRY. 

CoH,03-rH0. Formic acid also unites with bases to form salts, which closely 
resembles the acetates. 

141. Chloroform, CglLPJlj — Tllis substance > which is regarded as a 
terchloride of the radical fbrnayle, is best obtained by distilling alcohol, or 
wood-spirit, with a solution of chloride of lime (bleaching powder). It is an 
oily, colorless liquid, of an agreeable, ethereal odor, and of a sweetish taste. 
An alcoholic solution of chloroform, prepared by distilling chloride of lime 
with an excess of alcohol, is known in medicine by the incorrect name of 
chloric ether, and is the liquid which is now generally sold and used under 
the name of chloroform. The vapor of chloroform, when inhaled with atmos- 
pheric air, produces anaesthetic effects, like the vapor of ether. It is, how- 
ever, much more potent and agreeable than ether, and has to a considerable 
extent replaced the latter agent in surgical practice. Chloroform, unless pre- 
pared from perfectly pure alcohol, is liable to contain certain foreign and 
volatile compounds, which exert a most deleterious and often fatal effect upon 
the system when inhaled. No person, therefore, should sell or use chloroform 
which is not known to have been properly prepared. Chloroform is with 
difficulty kindled, and burns with a greenish flame.* 

742. Amylic Alcohol . — In the process of distilling whiskey from pota- 
toes, there is generated, in connection with the crude spirit, a volatile, oily body, 
possessing a pungent, disagreeable odor. This substance, the complete sep- 
aration of which from the crude spirit is a matter of difficulty, appears to be 
analogous, in its composition and chemical reactions, to alcohol, and is re- 
garded as the hydrated oxyd of a radical, termed amyle, — the hydrated oxyd 
itself being called amylic alcohol, or more generally, fusel oil (from the Ger- 
man fu-sclod), or oil of potato spirits.* Amylic alcohol, in a pure state, has the 
appearance of a thin, colorless oil ; it is highly volatile ; and the inhalation of 
its vapor, hi even a minute quantity, is attended with very deleterious effects; 
the fatal accidents which have sometimes resulted from the use of chloroform 
being generally ascribed to its admixture with this compound. It exists in 
almost all ordinary alcohol in small quantity, and is the occasion of the per- 
sistent and somewhat faintly-disagreeable odor which alcohol leaves upon a 
surface after evaporation. 

The extraordinary character of the compounds and derivatives of amylic 
alcohol (fusel oil), render it one of the most interesting products of organic 



* A most efficient and economical apparatus for disinfecting apartments and purifying 
the air, may be arranged by burning chloric ether in a simple camphene lamp provided 
with one wick. In dissecting-rooms, in cellars where vegetables have decayed, or where 
drains allow the e^cipe of offensive gases, and in outbuildings, no more effective and 
agreeable method of purifying the air can be resorted to. 

* Amyle derives its etymology from the Latin amylum, starch, the Bubstance being a 
product of the fermentation of starch. 

Questions. — What is chloroform? How is it prepared? What are its properties? 
AVhat is the so-called chloric ether? When is chloroform liable to be injurious? What 
is amylic alcohol ? What other name is applied to it ? What are its properties ? What 
is a characteristic feature of this substance ? 



ALCOHOL AND ITS DERIVATIVES. 449 

chemistry — most of the substances into which its constituents enter as compon- 
ents being characterized by very singular and remarkable odors. For example, 
when amylic alcohol is warmed, and dropped upon platinum black, it oxydizcs 
and forms an acid, which bears the same relation to its alcohol that acetic 
acid does to ordinary alcohol. This compound possesses in an intense degree 
the odor of valerian, and is believed, furthermore, to be identical with tho 
acid which imparts to the root of the plant valerian its odor and medicinal 
properties : it has hence been called valerianic acid, and has been advantage- 
ously employed in medicine in place of the natural extract. 

By distilling amylic alcohol, under proper circumstances, with various 
acids, Ave obtain odoriferous compounds, which, during the last few years, 
have becomo familiarly known as "fruit extracts," or " essences," and as 
"liquor flavoring materials." Thus amylic alcohol, distilled with sulphuric 
acid and acetic acid (acetate of potash), yields an oily product which possesses 
most perfectly the odor of the " Jargonelle" pear ; chromic acid, substituted in 
the place of acetic acid, gives oil of apples ; while other acids yield products 
possessing the flavors of the banana, the orange, and many other fruits. In 
the same manner, the flavoring principles which characterize spirituous liquors 
may be obtained, and indeed are now manufactured and sold extensively 
under the names of "oil of cognac" "oil of wine" etc., for the fabrication of 
almost any kind of liquor or wine, from pure alcohol.* Although prepared 
from a poisonous basis (fusel oil), these extracts do not appear to possess any 
injurious qualities, when used in moderate quantities as flavoring agents ; and 
the position has even been taken by some chemists that they are identical in 
composition with the perfumes which nature carefully elaborates in different 
fruits and plants. In addition to perfumes the most agreeable, however, 
odors of the most disgusting and nauseous character can also be produced 
by like means, as, for instance, the odor of the bed-bug, squash-bug, and of - 
many disagreeable plants and weeds. The basic radical employed for 'this 
purpose is not, however, in all instances amyle, as the same properties are 
characteristic to some extent of a number of analogous radicals. 

743. Sulphur Alcohols, or Mercaptans . — By various indi- 
rect processes, the oxygen of wine, methylic and amylic alcohol, may be re- 
placed by sulphur, their other constituents remaining unaltered, and in this 
way a series of bodies may be produced, which from their resemblance in 



* A few drops of oil of cognac, added to a glass of water colored with burnt sugar (car- 
amel), will convert it, so far as appearance and odor is concerned, into a fair article of 
dark brandy. Manufacturers, in fabricating spirituous liquors from alcohol, by tho 
aid of thise flavoring extracts, find it necessary to use an article of spirits from which 
every trace of fusel oil has been previously extracted, as this substance, in a separate 
state, seems to destroy flavoring extracts which contain its elements as constituents. This 
separation of fusel oil from alcohol is now accomplished by distilling the crude spirit in 
connection with permanganate of potash. 

Questions— "What is valerianic acid ? What are other derivatives of this body ? What 
are the so-called sulphur alcohols, or mercaptans? 



450 ORGANIC CHEMISTRY. 

composition to alcohol, have been called sulphur alcohols, or by reason of 
their great affinity for mercury, mercaptans (mercurium captans). Thus the 
composition of wine alcohol being C4H 6 2 , its mercaptan would be C 4 Ii6S 2 . 
These products in their properties closely resemble the oily compounds which 
impart to garlic, the onion, and other plants of like character their offensive 
odors, and in fact may be considered as artificial oils of garlic. The mer- 
captan produced from methylic alcohol is a colorless liquid, with a most of- 
fensive and concentrated odor 'of onions, which penetrates and obstinately 
adheres to every substance with which it is brought in contact. 

144. If we replace the sulphur existing in these fetid compounds with ar- 
cenic, we produce new volatile substances which are not only insufferable in 
their smell, but rank among the most deadly poisons known to chemists. 

Such a compound is kakodyle (from Kaitog, evil, and vTitj^ principle), formed 
by the union of arsenic with the radical methyle, and which, from the cir- 
cumstance that it fulfils in composition the part of an element in a very re- 
markable manner, has been studied by chemists with great minuteness.* 
United with cyanogen, it forms cyanide of kakodyle, a compound possessed 
of most deadly qualities. "When exposed to the air it rises in the form of 
vapor, which by contact with moisture is instantly decomposed, its arsenic 
uniting with oxygen to form fumes of arsenious acid, while the cyanogen by 
combination with hydrogen forms prussic acid ; and thus at the same in- 
stant the air is impregnated with vapors of the two most deadly poisons 
with which we are acquainted." The evaporation of a few grains of cyanide 
of kakodyle in the atmosphere of a room, is said to produce almost instan- 
taneous unconsciousness. In addition to these substances, many other com- 
pounds of a somewhat similar character have been formed and described, 
and it has sometimes been proposed to employ them as ingredients in ex- 
plosive war projectiles (asphyxiating bombs). 



CHAPTER XX 



VEGETABLE ACIDS. 



145. Over two hundred distinct acid compounds, the products of the 
vegetable kingdom, have been isolated and described by chemists. They are 
all composed of carbon, hydrogen, and oxygen, with the latter element gen- 
erally in large excess. They are not, however, usually found in plants in a 



* A recent chcmicn.l authority has described the odor of this compound as far exceeding 
in offensiveness the fetor exhaled by any animal or vegetable. 

Questions. — What are their properties ? By replacing sulphur with arsenic, what com- 
pounds are formed ? What is kakodyle ? What are its properties ? What is said of the 
number and distribution of the vegetable acids? 



VEGETABLE ACIDS. 



451 





free state, but in combination with various bases derived from the soil, such 
Fig. 230. as potash, soda, lime, etc. The salts Fig. 231. 

thus formed are sometimes neutral, but 
more frequently acid in their charac- 
ter, and consequently impart to the 
portions of the plant containing them 
a distinctly acid taste and reaction. 
"When the salt is sparingly soluble, it 
often accumulates in the cells of the 
plant in the form of minute crystals, 
which are readily discernible by the 
microscope. Fig. 230 represents crys- 
tals of lliis character found in the onion, and Fig. 231 crystals 
of oxalate of potash occurring in the rhubarb. 

Some of these acids are very widely diffused in the vegetable 
kingdom, but the majority occur in only a few particular plants, 
and in minute quantities. The most important of them only require special 
consideration. 

746. Oxalic Acid, C 2 3 II . — This acid is found abundantly in many 
plants in combination with potash and lime, and is the principle of acidity in 
the leaves of the sorrel and the rhubarb (pie-plant). It is also a constituent in 
certain minerals. For practical purposes it is prepared artificially by digest- 
ing sugar with strong nitric acid ; thus, when these two substances are gently 
heated in connection, in the proportion of 1 part of sugar to 8 of acid, violent 
action ensues, accompanied with a disengagement of copious fumes of nitrous 
acid ; and the solution remaining after the cessation of the action, furnishes, 
by evaporation, crystallized oxalic acid. Starch, woody fiber, and many other 
organic substances, treated in the same manner, yield the same product. 

In its pure state, oxalic acid is a crystalline solid, not unlike Epsom salts, for 
which it is not unfrequently mistaken. It possesses, however, an intensely 
sour taste (which Epsom salts does not), is freely soluble in water, and when 
taken internally, is highly poisonous, occasioning death in a few hours. The 
proper antidote for it is the administration of chalk or magnesia, suspended in 
water. 

Oxalic acid is extensively employed in calico-printing, and to some extent 
by straw and Leghorn bonnet-makers, for the purpose of cleansing their 
wares. It is also used in chemical analysis as an exceedingly delicate test 
for the presence of lime, or any of its soluble compounds. The salts formed 
by oxalic acid are termed oxalates. Binoxalate of potash, which is often ex- 
tracted from certain species of sorrel, is sold under the name of "salts of sor- 
rel," or "essential salts of lemons," for the purpose of discharging iron-rust, or 
ink-stains from linen. Its use for this purpose depends upon the fact, that 



Questions "What is said of the occurrence of oxalic acid ? How is it obtained for in- 
dustrial purposes? What are its properties ? What its uses ? What are its salts called ? 
What are salts of sorrel or of lemons ? How are they operative in removing ink-stains? 






452 OKGANIC CHEMISTRY. 

oxyd of iron (the basic coloring matter of ink) is readily soluble in oxalic acid, 
and therefore leaves the fiber and forms an oxalate of iron. The corrosive 
powers of the acid are not sufficient to injure the fibers of the linen, if it be 
speedily removed by washing. 

747. Tartaric A c i d , Cs H 4 0i , 2j[0 , in combination with potash, 
exists in many fruits, and is especially the acid principle of grapes. When 
the expressed juice of the grape is fermented, as in the manufacture of wine, 
the tartaric acid, in combination with potash, forming an impure tartrate of 
potash, gradually separates from the liquor, and deposites itself as a crust 
upon the interior of the casks, and in this condition is known in commerce as 
argots, or crude tartar. The pure acid obtained from this source is a white, 
crystallized solid, freely soluble in water, and of an agreeable, acid taste. 

Tartaric acid forms with potash two salts, — the neutral tartrate, containing 
2 atoms of alkali to 1 of acid, 2KO, CgTLiOio ; and the acid, or bi-tartrate, in 
which an atom of potash is replaced by an atom of water, thus, KO, HO, Cs 
H4O10. This latter salt is the well-known " cream of tartar." By saturating 
a solution of cream of tartar with soda, a double tartrate of potash and soda 
is formed, which is extensively used in medicine as a mild purgative, under 
the name of " Rochelle salts," or " powders." Tartaric acid, mechanically 
mixed with bi-carbonate of soda, constitutes the so-called " soda powders," or 
the ingredients of the ordinary effervescing draughts. Tartaric acid is chiefly 
employed in dyeing. 

748. Citric Acid is the principal acid which imparts sourness to the 
lemon, orange, and the cranberry ; but also exists in many other fruits, as the 
currant, gooseberry, etc. It is readily obtained from the juice of the lime and 
lemon (citron), and is used in calico-printing, in medicine, and in domestic 
economy, as a flavoring material. Citric acid, by heating, passes into aconitic 
acid, an acid which occurs native in the plant called " monk's hood." 

749. Malic Acid was first obtained from the juice of the apple (hence 
its name from the Latin malum, an apple). It is the most widely diffused of 
all the vegetable acids, and is the cause of acidity in most unripe fruits. For 
practical purposes it is usually obtained from the berries of the mountain-ash, 
though it exists abundantly in the stalks of the rhubarb, in the pear, the 
cherry, the raspberry, the strawberry, and many similar fruits. 

750. Tannic Acid, or Tannin, is the general name given to various 
substances (probably of somewhat different composition), which are exten- 
sively diffused in plants, and which are characterised by a well-known puck- 
ering and astringent taste. They are regarded as acids, since they possess an 
acid taste, and are capable of uniting with bases to form salts. Tannic acid 
exists in almost all vegetables, in the bark and leaves of trees, and in the 
seeds of fruits. It is, however, most abundant in the bark of the oak and the 

Questions. — What is said of tartaric acid ? What are argals ? What is cream of tar- 
tar? What are Rochelle powders ? What are soda powders ? What is said of citric acid ? 
What of malic acid ? What is tannin or tannic acid ? In what substances is tannin most 
abundant ? 



VEGETABLE ACIDS. 453 

hemlock, in the fruit and stems of the sumach, and especially in nut-galls, 
which are excrescences produced upon the branches and leaves of certain spe- 
cies of oak, by the puncture of insects. Green and black teas contain from 8 
to 10 per cent, of tannin, which imparts to them their strong, astringent qual- 
ities. Tannic acid is freely soluble in water, and is readily obtained in solu- 
tion, by digesting the portions of the plant containing it in water. 

751. Leather . — The most remarkable feature of tannic acid, is its prop- 
erty of uniting and forming insoluble compounds with albumen, gluten, gela- 
tin, and with the skin and tissues of animals in general. Such compounds 
will not putrefy, and are unchangeable in water. This principle is practically 
applied in the manufacture of leather, which is effected by steeping the skins 
of animals, which consist chiefly of gelatin, in aqueous infusions of barks 
containing a large percentage of tannic acid.* Some varieties of skins may 
be tanned in a few days, or even hours; but for the production of the best 
qualities of leather, they are allowed to remain in contact with the tan liquor 
from 9 to 15 months, and often for a period of years. 

152. Inks. — When a solution of tannin is brought in contact with salts 
of the sesquioxyd of. iron, it yields a deep bluish-black precipitate — the per- 
tannate of iron-^r.which is extensively employed for dyeing fabrics of a black 
or brown cojor, and in the manufacture of inks. Common writing-ink is 
formed blading to a clear infusion of nut-galls a solution of protosulphate of 
iron (copperas). To prevent the precipitate from settling, and for thickening 
the fluid, a mucilage of gum-arabic is also added. Ink thus prepared consists 
at first principally of the tannate of the protoxyd of iron, and is too pale for 
use ; by exposure to the air, however, it gradually absorbs oxygen, and is 
converted into the tannate of the sesquioxyd — the liquid, at the same time, 
deepening in color, and finally becoming black. Mouldiness in ink may be 
prevented by the addition of a small quantity of the oil of cloves, creosote, or 
corrosive sublimate : the latter, in small amount, is probably more efficient 
than all the others ; but it should be remembered that it is a deadly poison. 
Faded writings can be restored in a measure by washing them with an infu- 
sion of galls, f 

* Oak bark contains from 5 to 6 per cent, of tannin ; and in this, as well as in all other 
astringent barks, the tannin is contained solely in the inner, white layers, next to the sap- 
wood, or alburnum. From 4 to 6 pounds of oak-bark are required for the production of 1 
pound of leather. Leather tanned with oak-bark is considered superior to that made from 
any other tanning material, but the process is slower. Nut-galls contain more tannic acid 
than any other substance, the quantity varying from 30 to 40 per cent. Sumach is used in 
the manufacture of the lighter and finer kinds of leather. Sicilian sumach contains about 
16 per cent, of tannin, and that grown in the United States from 5 to 10 per c.ent. 

t The cause of the browning and fading of ordinary inks, results chiefly from a per- 
oxygenation of the iron, and its separation from the acid combined with it. No salt of 
iron, and no preparation of iron, equals the common sulphate (that is, commercial cop- 
peras) for ink-making, and the addition of any persalt, such as the nitrate or chloride of 

Questions. — What is its most remarkable property ? How is leather prepared ? What 
is the reaction of tannin with sesquioxyd of iron ? How iB ink prepared t Why does ink 
grow dark by exposure to the air? 



454 ORGANIC CHEMISTRY. 

The permanent black color of the grain side of the leather used in the 
manufacture of boots and shoes is also a tannate of iron, produced by wash- 
ing the leather when in a moist state with a solution of the acetate of the 
sesqui-oxyd of iron. 

753. Gallic Acid . — This acid is found naturally associated with tan- 
nin in vegetable tissues, and is also formed from tannic acid by exposing 
a solution of the latter for some time to the action of the air. It pi educes, 
like tannin, a dark precipitate with the salts of the sesqui-oxyd of iion, but 
does not unite with gelatin to form insolubb compounds, and is consequently 
of no value for the manufacture of leather. When added to the salts of 
silver, gold, and platinum in solution, it occasions a precipitation of the metal 
in a state of minute subdivision. The most successful compounds for colcr- 
ing the hair are founded upon this principle — the hair being wet in the first 
instance with a solution of gallic acid, and afterward with a solution of a 
salt of silver in ammonia. The reduced metal imparts to the hair a fine 
black or brown color, which is extremely permanent. 

In addition to the substances mentioned which afford tannin, there are 
several others which afford it and constitute important articles of commerce. 
Among them may be mentioned the following : catechu, cutch, and terra japon- 
ica are the dried aqueous extracts of a species of acacia growing in India ; kino 
is a product of like character ; divi-divi is the pod o£ a leguminous shrub, 
a native of South America. These substances will be found mentioned in 
almost every commercial price current. The best gall nuts are exported from 
Asia Minor. 

In addition to the acids which are secreted by living vegetable tissues, a 
great number have been also recognized by chemists which do not exist natu- 
rally in plants, but are the result of vegetable decompositions taking place 
either under natural or artificial conditions. The acids included in the sub- 
stance called humus, and many of the products resulting from the action of 
mineral acids upon the constituents of coal-tar, are examples of this nature. 



iron, or of logwood, impairs the durability of the ink. Experiments recently detailed to the 
Scottish Society of Arts, show that the quality and durability of ink is greatly increased, 
however, by the addition to it of a small quantity of sulphate of indigo, and the following 
receipt was given as affording an ink that was superior to all others for writing pur- 
poses: 12 ounces powdered nut galls, 8 ounces sulphate of indigo, 8 ounces of copperas, a 
few cloves, and 4 to 6 ounces of gum arabic per gallon of ink. Documents written with 
steel pens are less durable than those written with quill pens, as the contact of iron or 
steel with ink, injures it to a greater or less extent. 

Questions. — How is a black color given to leather ? What is said of gallic acid ? 
What are its characteristic features ? What products are commercially important on ac- 
count of their tannin? What other acid compounds are considered in this connection ? 



ORGANIC ALKALIES. 455 

CHAPTER XXI. 

ORGANIC ALKALIES. 

754 The terms organic alkalies, vegetable alkaloids, and organic bases, are 
applied to a peculiar class of organic substances which resemble in certain 
of their properties the alkalies of inorganic chemistry ; that is to say, they 
neutralize acids, unite with them to form salts, and in most instances, when 
in solution, restore the blue color of reddened litmus. They all contain nitro- 
gen as an essential constituent, and are exceedingly complex in their consti- 
tution. They are sparingly soluble in water, but dissolve freely in hot alco- 
hol, from which they often crystallize on cooling in a very beautiful manner. 
The taste of these substances in solution is usually intensely bitter, and the 
majority of them are active and virulent poisons; when given, however, 
in small doses, they rank among the most powerful medicines. 

Of the organic alkaloids, about one hundred are now known to exist in 
plants as natural products, always in combination with vegetable acids. They 
were formerly supposed to be exclusively the result of vegetable organiza- 
tion, but within a comparatively few years some seventy or eighty compounds 
of a similar character have been artificially prepared from organic products by 
chemists. These last are termed the artificial organic alkaloids, and do not 
occur in nature. The true vegetable bases have not yet been artificially imi- 
tated. 

Most of the vegetable alkaloids are prepared by boiling the vegetable mat- 
ter containing them in water acidulated with hydrochloric acid, when the 
alkaloid unites with the acid to form a soluble salt, and enters into solution. 
From this it is precipitated in a separate state hy the addition to the liquid 
of a stronger base — i. e., lime, potash, ammonia, etc. The plants which by 
treatment furnish alkaloids, are generally characterized by possessing poison- 
ous or active medicinal qualities, which in turn are supposed to be due to 
the alkaloids contained in them. The following are some of the most impor 
tant of the alkaloids extracted from vegetable products. 

755. Morphia . — Morphine. — This alkaloid is the chief active principle 
of opium, which is the dried juice of certain species of the poppy. It exists 
in opium in combination with meconic acid, and the best qualities of opium 
contain about ten per cent, of it. It crystallizes in small, colorless prisms, i3 
devoid of smell, and possesses a bitter, unpleasant taste. It is powerfully nar- 
cotic and poisonous, and is an invaluable remedy in medicine, in small doses, 
for soothing nervous irritation and allaying pain. A full dose of pure morphia 



Questions. — What are the organic alkalies? By what other names are they desig- 
nated? What are the general properties of these substances? What is their number? 
Are any of them prepared artificially ? How are the vegetable alkaloids obtained ? What 
are characteristics of the plants which furnish them? What is morphia? What is 
opium ? What are the properties of morphia ? 



456 ORGANIC CHEMISTKY. 

for a grown man is one eighth of a grain ; and in the state of acetate or muriate of 
morphia (in which condition it is generally used in medicine) one fourth of a 
grain. It is a singular circumstance that this substance, which is so poison- 
ous to man, has comparatively little effect upon animals, even when adminis- 
tered in large doses. The composition of morphia is represented by the formula, 
C 35 H 20 NO 6 + 2HO. 

Opium also contains, in addition to morphia, eight other alkaloids, the prin- 
cipal of which are termed narcotine, meconine, and thebaine. They are all nar- 
cotics and poisons, and exist to some extent in laudanum, which is an alco- 
holic extract of the active principles of opium. 

756. The dried juice of the common lettuce plant has considerable resem- 
blance to opium, and contains an active principle (supposed to be an alkaloid), 
called lactucin. It is this substance which gives to lettuce, when freely eaten 
as a salad, its narcotic properties. 

757. Q u i q i n e and Cinchonine are the alkaloids which impart to 
Peruvian bark its medicinal virtues. Quinine is a white, crystallized sub- 
stance, of an intensely bitter taste. It is one of the most valuable and reliable 
of medicinal agents, and is generally administered in the form of a sulphate. 

758. Strychnia and B r u c i a are extracted from a variety of plants 
belonging to the genus strychnos, and especially from the berries (nux vomica) 
of a small tree of this genus growing in India. These alkaloids are remarkable 
for being the most powerful of all vegetable poisons — a single grain of the 
former being a fatal dose for an adult man ; while a sixth of a grain has proved 
fatal to a dog in thirty seconds. Its influence seems to be exerted principally 
upon the nerves and spinal marrow, producing violent spasms, which increase 
in frequency and severity until death. The celebrated woorara with which 
the natives of Guiana, S. A., poison the tips of their arrows, and the poison 
of the celebrated Upas tree of the island of Java, are varieties of strychnias. 

Pure strychnia crystallizes in small, but exceedingly brilliant, colorless 
crystals, and is slightly soluble in water. It possesses the property of bitter- 
ness in a more marked degree, probably, than any other substance, and its 
taste can be distinctly recognized when dissolved in 600,000 times its weight 
of water. Vegetable matters containing this alkaloid are sometimes employed 
for imparting bitterness to beer, but their use should be considered criminal. 

759. Among the other important alkaloids may be mentioned Nicotine, tho 
poisonous principle of tobacco ; Aconitine, or Aconite, extracted from the plant 
"monk's hood;" Conicine, prepared from hemlock; Veratrine, from the plant 
hellebore ; Hyoscyamine, from henbane ; and Solanine, from several species 
of the genus solanum, and from the white sprouts of the potato. All these 
are most virulent poisons, only inferior in their action to strychnia and brucia. 

Questions. — What is its composition ? What is laudanum ? Is there an activo prin- 
ciple in the lettuce plant? What are quinine and cinchonine? From what sources are 
strychnia and hrucia obtained ? For what are these alkaloids remarkable ? What is said 
of the poisonous influence of strychnia ? What are varieties of this poison ? What are 
the other properties of strychnia ? What are some of the other alkaloids remarkable for 
their poisonous qualities? 



ORGANIC COLORING PRINCIPLES. 457 

Among the alkaloids less injurious in their action on the animal economy, are 
Emetine, the medicinal agent of ipecac (ipecacuanha); Piperine, extracted 
from ordinary black pepper ; and Caffeine, or TJieine, the enlivening principle 
in coffee and tea. 

The organic alkaloids are, almost without exception, precipitated from their 
solutions, by tannic acid, in the form of insoluble tannates, and consequently 
the most efficient remedies in cases of poisoning by them, are liquids contain- 
ing tannic acid, such as decoction of oak-bark, tincture of gall-nuts, concen- 
trated infusion of green tea, etc., etc. 

The detection of their presence in the animal organism, in cases of death by 
poisoning, is extremely difficult, strychnia excepted, and the testimony of the 
most experienced chemists ought only to be relied on in such cases.* 

760. Vegetable Extracts , — This name is applied to a very large 
class of substances extracted from plants, which do not possess sufficiently 
marked features, in a chemical point of view, to allow of their incorporation 
with any of the more well-defined groups of organic compounds. Some of 
them, however, possess active and medicinal properties, as, for example, the 
intensely bitter principle of wormwood, aloes, etc., the purgative principle of 
tho root of the rhubarb, and the aromatic bitter of the hop, sweet-flag, etc. 
They have for the most part a bitter taste, and often occur crystallized ; and 
are generally regarded as mixtures of various vegetable products. 



CHAPTER XXII. 

ORGANIC COLORING PRINCIPLES. 

761. The organic coloring matters, with the exception of the red dye ob- 
tained from cochineal, are all of vegetable origin. They do not, as a class, possess 
many chemical characters in common, and are considered under one general 
head, by reason of their common industrial applications. Many of the most 
valuable vegetable coloring agents do not exist naturally in plants, but aro 
formed by subjecting certain vegetable products to specific chemical treat- 
ment. The most brilliant and splendid of the vegetable colors, as those of 
flowers, for example, are exceedingly evanescent, and are generally destroyed 
by any treatment employed to extract them ; they also exist in the vegetable 



* A few years since a man was convicted in Albany, N.Y., of murder, by tbe adminis- 
tration of tincture of aconite, upon what was supposed to be reliable chemical testimony, 
but which was afterward shown to be so utterly unreliable, that the means adopted for 
detecting the poison must have completely removed it, if present, from the matters 
tested. 

Questions. — What are more medicinal than poisonous? What are antidotes for these 

poisons? What is said of their detection in the system? What are vegetable extracts? 

What examples of these substances ? From what source do we derive organic coloring 
agents ? What is said of them ? 

20 



458 ORGANIC CHEMISTRY. 

tissue, in very minute quantities. Coloring matters extracted from those parts 
of the plant which are removed from the immediate influence of the light, as 
the wood, bark, etc., are much more permanent, but less brilliant. 

162. The art of dyeing consists in impregnating cloths and other textures 
with coloring substances, in such a maimer that the acquired colors may re- 
main permanent under the common exposure to which the articles may bo 
liable. This is effected by producing a chemical union between the materials 
to be dyed and the coloring matter. Different fibrous materials present very 
different attractions for dye-stuffs, and absorb coloring matter in very differ- 
ent proportions : wool appears to have the greatest attraction ; silk comes 
next to it ; then cotton, and, lastly, flax and hemp. "While the former, there- 
fore, are dyed with very little difficult} 7- , the latter can only be made to per- 
manently combine with coloring substances, through the agency of indirect 
and complicated processes. 

7G3. All coloring substances used, in dyeing are divided into two classes, 
viz., substantive and adjective colors. A substantive color is one that imparts its 
tint directly to the substance to be dyed, without the intervention of a third 
substance. An adjective color, on the contrary, is one that requires the inter- 
vention of a third substance, that possesses a joint attraction for the coloring 
principle and for the substance to be dyed. 

Most of the substances used in dyeing belong to the adjective colors; and 
if we except indigo, there is scarcely a dye-stuff in extensive use that imparts 
its own color directly ; and by far the greater number of dyes have so weak 
an affinity for cotton fabrics, that alone they communicate no color sufficiently 
permanent to deserve the name of a dye. 

The intermediate third substance which is used to effect a union between 
the dye and the cloth, is called a mordant, from the Latin word mordeo, to 
bite, from an idea the old dyers had that these substances bit or opened a 
passage into the fibers of the cloth, and allowed the color to penetrate. Tho 
action of a mordant may be illustrated by the method of procedure followed 
in dyeing cottons black, by an extract of logwood. An aqueous solution of 
logwood is very deeply colored, but imparts no permanent dye to cotton. If, 
however, the cotton be previously impregnated with a salt of ox} r d of iron (as 
copperas), and then dipped into the extract of logwood, the coloring principle 
of the latter, by reason of its great affinity for oxyd of iron, unites with it, and 
the two are precipitated upon the fibers of the cloth in the form of a black pre- 
cipitate or dye. A dye thus effected is usually a fast color, since it is 
formed in and incorporated with the whole structure of the fiber itself, and is 
not merely upon its surface ; so that the color will only disappear when the 
texture and fiber of the cloth are destroyed. The use of mordants, further- 



Qtjebtions. — In what does the art of dyeing consist? What fibrous substances have the 
greatest attraction for dyes? Into what two classes may dyeiug principles be divided? 
What are substantive colors ? What are adjective colors? To which class do the dyes in 
ordinary use generally belong ? What is the derivation of the word mordant ? Explain 
the use of mordants ? 



OKGANIC COLORING PRINCIPLES. 459 

more, adds greatly to the resources of the dyer ; because a single coloring 
substance will impart very different colors with different mordants : thus, an 
extract of logwood will dye with iron, black ; with a solution of tin, -violet ; 
and with other mordants, all the shades of color included between a yellowish- 
white and a violet, a lavender and a purple, or a slate-brown and a black. 

764. Calico-Printing . — The general process of calico-printing is aa 
follows : The cloth is first prepared, by bleaching and other treatment, to re- 
ceive the colors. The pattern is then stamped or printed upon it from plates 
or rollers, which have been previously covered with different mordants, in the 
same way that ink is applied to types. The cloth is then passed through a 
solution of dye, when those parts which have been printed with the mordant 
seize upon and retain the colors. The cloth is afterward washed, when all 
the color not combined with mordant disappears from its surface, and the pat- 
tern impressed is brought out with distinctness. 

765. The most important coloring matters used in dyeing are as follows: — 
Red and Violet Coloring Substances. — Madder is the 

ground-up root of the plant rubia tinctorum. Its most beautiful coloring con- 
stituent (madder red, Turkey red), called garancine, is not a natural product, 
but results from subjecting the root to the action of sulphuric acid. The ac- 
tion of the acid in this instance is often cited as an example of catalysis, as it 
does not enter into combination with the coloring principle of the root, but 
effects a change in it, apparently by its mere presence. 

Madder is used to a greater extent in dyeing and printing cottons than any 
other substance, and with different mordants it furnishes very bright and 
durable reds, yellows, violets, and browns. The other important coloring 
substances of this class are "Brazilwood," " safflower" (the flowers of the red 
caffron), sandal- wood (" red-sanders"), and cochineal. The last is a dried 
insect, the cocus cacti, which lives upon several species of cactus, peculiar to 
warm latitudes, and especially to Central America. It yields the most bril- 
liant scarlet and purple colors. 

766. Blue Dyes, Indig o. — The most important of the blue dyes is 
Indigo, which is obtained from several species of American and Asiatic plants, 
particularly from those belonging to the genus indigo/era. The juice of these 
plants is colorless, but when their leaves are digested in water, and allowed 
to ferment, a yellow coloring substance is dissolved out, which, by exposure 
to the air, gradually becomes blue, and is deposited from the solution in the 
form of a thick sediment. This washed and dried, constitutes the indigo of 
commerce. 

Commercial indigo is far from pure, and in addition to the blue coloring 
matter, or pure indigo, it contains at least one half its weight of foreign sub- 
stances. Pure indigo is quite insoluble in every liquid, with the exception of 

Questions. — How do they increase the resources of the dyer ? What is the process 
of calico-printing? What is madder ? What is said of its coloring principles ? What is 
cochineal? What colors does it furnish? What other dye-stuffs furnish red colors? 
What is the most important of the blue dyes ? How is indigo prepared ? 



460 ORGANIC CHEMISTRY. 

fuming sulphuric acid (Nbrdhausen), with which it forms a compound quite 
soluble in water, called sulphindigotic acid. When indigo is brought in con- 
tact with water and deoxydizing agents, it becomes converted into a soluble 
and colorless substance, known as indigo white, which, by exposure to the air, 
again absorbs oxygen, and resumes its blue color. This circumstance is taken 
advantage of in dyeing ; thus, the indigo is mixed, in a state of fine powder, 
with hydrate of lime and copperas, and the whole digested in water. Under 
these circumstances, the hydrated protoxyd of iron, resulting from the action 
of the lime, abstracts oxygen from the indigo, and reduces it to a state of a 
yellow liquid (white indigo). Cloths steeped in this liquid, and exposed to the 
air, readily acquire a deep and permanent blue tint, by the formation of the 
blue, insoluble indigo in the substance of the fibers, and it is in this way that 
the fine indigo-blue colors are produced. "What is called Saxon blue, a brighter 
color than ordinary indigo, is imparted by boiling the fabrics in sulphindigotic 
acid. Among other prominent blue dyes, may be mentioned litmus, which is 
obtained from several species of lichens, by treatment with ammonia — the 
plants themselves being destitute of color. Archil and cudbear are substances 
allied to litmus. 

767. Yellow Coloring Substances. — The most valuable dye- 
stuffs of this class are fustic, the rasped wood of a "West Indian tree ; querci- 
tron, obtained from the bark of the American black oak ; the berries of the 
buckthorn; annotto, prepared from the pulp of certain South American 
seeds ; and tumeric, the root of an East Indian plant. 

768. C h 1 o r o p h y 1 e is the name given to the green coloring matter of 
the leaves and stems of plants. It exists in them in very small quantity, and 
is extracted with difficulty in a state of purity. It appears to be united in 
the vegetable tissue with a substance resembling wax, and is insoluble in 
water, but dissolves in alcohol and ether ; hence all tinctures in pharmacy, 
prepared from the fresh stalks and leaves of plants, possess a green color. 
Chlorophyle appears only in those parts of plants which are exposed to the 
action of fight ; hence this agent is supposed to exercise an important and 
direct influence on its formation. Plants grown in the dark are nearly des- 
titute of color, but when removed into the sunlight become rapidly green. 
The red and yellow colors which leaves assume in autumn, are supposed to 
be due to the decomposition and oxydation of the chlorophyle, and the for- 
mation of an acid compound; but the information we possess on this subject 
is very limited. 

Most of the greens used in dyeing are of a mineral origin, i. e., the salts 
of chromium and of copper. 

No genuine black substantive color has ever been obtained from plants. 

Questions. — What is said of the solubility of indigo? What is indigo white ? How is 
it employed in dyeing? How is ''Saxon blue" imparted? What other blue dyes are 
used ? Enumerate some of the principal yellow dye-stuffs ? What is chlorophyle ? What 
are its solvents ? What agent influences its formation ? What is the character of the 
greens used in dyeing ? 



OILS, FATS, AND RESINS. 461 



CHAPTER XXIII. 

OILS, FATS, AND RESINS. 

769. Connection between Oils and Fats . — The oils and 
the fats, whether of animal or vegetable origin, are regarded as belonging to 
the same general class of organic substances ; and with the exception of the 
volatile oils, they are all closely allied to each other in their chemical properties, 
anl are composed of the same elements, viz., carbon, hydrogen, and oxygen, 
united in various proportions. As a class, they are all, however, character- 
istically poor in oxygen, but rich in hydrogen, and some few of the volatile 
oils contain no oxygen. The distinction between a fat and an oil is founded 
merely upon the circumstance, that the former is solid at ordinary temper- 
atures, while the latter continues more or less Horrid ; an oil, therefore, may 
be called a liquid fat, or a fat a solid oil. 

The fats and the oils are all highly combustible, and burn with a brilliant 
flame ; they are insoluble in water ; but dissolve with more or less readi- 
ness in alcohol or ether, and when brought in contact with paper leave a 
greasy mark, and render the paper translucent. The oily substances secreted 
by plants, are principally accumulated in the seeds and coverings of the fruit, 
although no portion of the plant is entirely destitute of them. The propor- 
tion existing in some seeds is very considerable. Thus flax-seed contains 
about 20 per cent, of oil, Indian corn 9 per cent, rape-seed 30 to 40 per cent., 
while the seed or bean which furnishes castor oil contains as much as 60 per 
cent. 

770. Division of the Oils , — All oily substances are divided into 
two classes, viz., the fixed and volatile oils ; the former when exposed to the 
air do not diminish in bulk, while the latter under the same circumstances, 
readily evaporate. 

771. Volatile Oils . — The volatile oils do not possess the greasy 
feel of the fat oils, and are almost always characterized by a strong aromatic 
odor, and a pungent burning taste. Many of them, also, are highly poisonous. 
"With alcohol they form solutions called " essences" and from this circumstance 
the oils themselves are very frequently termed " essential." They also dis- 
solve in ether and acetic acid, and mix in every proportion with the fixed or 
fat oils. They do not, however, like the fat oils, form soaps, but when ex- 
posed to the air they are frequently changed by the absorption of oxygen, 
and converted into resins. 

These oils (with the exception of a few which have been formed ar- 

Questions.— What is said of the class of oils and fats? What of their composition? 
What constitutes the difference between an oil and a fat ? What are their properties ? 
What is said of the distribution of the vegetable oils ? Into what two classes are oily 
substances divided? What are the characteristics of the volatile oils? What are es- 
sences ? From what sources are the volatile oils derived ? 



462 ORGANIC CHEMISTRY. 

tificially) are almost exclusively the products of the vegetable kingdom, and are 
generally obtained by distilling the plant with water ; in some instances, how- 
ever, they are extracted from the cellular tissue containing them by pressure, 
as in fresh orange or lemon peel. The boiling points of almost all these oils 
are above that of water, but their vapors are carried over mechanically in 
distillation by steam at 212° F., and condense with it in the receiver. In 
this way are obtained the oils of roses, orange flowers, lemons, lavender, win- 
ter-green, peppermint, and many others which in smell and taste more or 
less resemble the fresh plants from which they are derived. The greater 
portion of the oil floats upon the surface of the water which distils over with 
it, but the latter usually retains a small quantity of the oil in solution, and 
thus acquires its peculiar taste and odor. "Waters thus impregnated are 
termed "medicated," or " perfumed waters ;" rose-water, lavender-water, 
peppermint- water, etc., being examples of this character. 

The various perfumes and odors which plants emit, are believed to be 
mainly due to the presence of some one or more of the volatile oils in their 
structure, which gradually evaporate, and diffuse themselves in the atmos- 
phere. The quantity of oil, however, yielded by some plants which possess a 
marked odor, is exceedingly small — a thousand fresh roses, for example, af- 
fording by distillation less than two grains of oil (attar of roses). In some 
flowers, as the jasmin, the violet, and the tuber rose, the oil which imparts 
fragrance is, moreover, so evanescent and delicate, that it is destroyed by 
any process of distillation, and in such cases the perfume is obtained by ar- 
ranging the flowers in layers between cotton imbued with some fixed oil ; 
which latter gradually absorbs the volatile oil or perfume of the flower, and in 
turn imparts it to alcohol — thus forming an odoriferous essence. Patty bodies 
perfumed in this way have received the name of pomatums. 

The volatile oils do not appear to be uniformly diffused throughout the 
whole plant. In the mint and thyme they reside principally in the leaves and 
stems ; in the sandal and cedar trees they are in the wood ; in the rose, vio- 
let, etc., in the leaves of the flower ; in the vanilla, anise, and carraway, they 
are in the seed ; andln the ginger and sassafras in the root. Different parts 
of the same plant not unfrequently furnish different oils ; thus, the flowers 
of the orange-tree furnish one kind, the leaves another, and the rind of the 
fruit a third. 

772. Composition of the Volatile Oils. — The volatile oils 
differ materially from each other both in their composition and chemical re- 
actions, and are conveniently divided into three classes, viz., those composed 
of carbon and hydrogen only; those composed of carbon, hydrogen, and 0x3-- 
gen ; and those which contain in addition sulphur and nitrogen. Most of 
them contain at least two proximate principles, one of which, termed $<•$£$&* 

Questions. — How are they obtained ? What are medicated waters ? What is supposed 
to be the origin of the odors of plants ? What of the quantity of volatile oils yielded by 
plants? What are pomatums? Are the volatile oils uniformly diffused throughout 
plants ? Illustrate this. What is said of the composition of the volatile oils? 



OILS, FATS, AND RESINS. 463 

tene, is less fusible than the other, and may be separated by cold in the form 
of a camphor-like substance. The more liquid constituent, termed e laioptene , 
on the contrary, may be often obtained in a separate condition by distilla- 
tion at a low temperature. 

773. Oils composed of Carbon and fl y d r og e n.— This 
class embraces a large number of the odoriferous essences of plants, and fur- 
nishes some of the most remarkable examples of isomeric bodies known in 
chemistry. Thus, the oils of turpentine, lemons, oranges, juniper, copaiba, 
citron, black pepper, and many others which possess entirely different prop- 
erties, contain exactly the same constituents, united in exactly the same 
proportions — 100 parts of each by weight containing 88*24: of carbon and 
1T76 of oxygen. These proportions are expressed by the formula OH*, or 
by some multiple of it, as 2(C5ll4). In addition to their identity in chemical 
composition, these substances also agree as regards their density and boiling 
points. The fact, however, that the internal arrangement of their molecules 
or particles is different, is strikingly shown by their diverse influence on a ray 
of polarized light, some of them causing it to diverge to the right, some to 
the left, while others transmit it unaltered, or directly. 

774. Oil or Spirits of Turpentine . — This substance, which 
may be regarded as the type or representative^ of the volatile oils containing 
omy4aa&gJW&ndlrvdro|£en, is obtained by distilling with water the semi-fluid 
sap or pitch called in commerce crude turpentine, which exudes from incisions 
made in the wood of various species of pine. The product left after distil- 
lation is a resinous solid, which is popularly termed r osin. 

Oil of turpentine is a thin, colorless liquid, which is highly inflammable, 
and possesses a well-known and powerful odor. It has a specific gravity of 
86, and boils at i?12 ° F. It is nearly insoluble in water, but dissolves freely 
in alcohol or ether. 

Camphene, which is extensively used in lamps as a substitute for oil, is 
spirits of turpentine purified by repeated distillations. Burning fluid is a so- 
lution of rectified turpentine or camphene in alcohol — the tendency of the 
turpentine to smoke being diminished by the addition of alcohol. 

Camphene and burning fluid, although highly inflammable, are not in them- 
selves explosive ; a mixture, however, of the vapor of these liquids with at- 
mospheric air is highly explosive, and igniting at a distance at the approach 
of the slightest spark or flame, is apt to communicate fire to the liquids them- 
selves. Burning fluid being much more volatile than camphene. is much more 
dangerous, and its use as an illuminating material should be discountenanced 
and forbidden. The explosive character of the mixture of its vapor and air 
may be illustrated without danger by allowing a small quantity of the fluid 

Questions. — "What is the first class remarkable for ? What are examples of this fact ? 
What substance is regarded as the type of this class ? How is turpentine obtained ? What 
is the residue left after distillation ? What are the properties of oil of turpentine? What 
is camphene ? What is burning fluid ? Are these liquids explosive? Why then i£ their 
employment so dangerous ? What is the comparative volatility of the two ? What ex- 
periment illustrates the explosive character of the mixed vapor of burning fluid and air ? 



464 ORGANIC CHEMISTRY. 

to evaporate in a tin can or vial, and then applying a lighted taper to the 
mouth. If, however, the mouth of the can be tightly corked,' under these 
circumstances, and flame be applied through a minute orifice in the side, an 
explosion of great violence is occasioned. ' As a matter of ordinary precau- 
tion in using these liquids, no attempt should ever be made to fill or replen- 
ish lamps that are lighted, neither should any vessel containing camphene 
or burning fluid be ever opened in the vicinity of a flame. 

When a current of dry hydrochloric acid gas is passed through oil of tur- 
pentine cooled by a freezing mixture, a white solid is formed which resembles 
common camphor in odor and appearance, and is termed artificial camphor. 
It is from this circumstance, probably, that the term camphene, as applied to 
spirits of turpentine, first originated. 

Oil of turpentine is extensively used as a solvent for resins in the manu- 
facture of varnish, in the preparation of paints, and to some extent in medi- 
cine. Many substances, also, like India rubber, etc., which are insoluble in 
alcohol, readily dissolve in it. 

The other more important oils of this class have been mentioned above 
as isomeric with oil of turpentine. 

775. Essential Oils containing Oxygen. — The principal 
oils of this nature are the oil of bitter almonds, of cinnamon, of roses, lavender, 
bergamot, and peppermint. In this class the proportions of the several con- 
stituents are rarely the same in two different oils. 

Common camphor, prepared by distilling the wood of the camphor-tree 
(found principally in Borneo and Japan), is regarded as a solid oil, or vola- 
tile fat of this class. It partakes of the general properties of the volatile oils, 
may be distilled without decomposition, and evaporates in the air at ordinary 
temperatures. It is nearly insoluble in water, but dissolves freely in alco- 
hol, forming what are termed camphorated sph its. On adding water to this, 
nearly all the camphor is thrownaown in a minutely divided state. Camphor 
taken internally in other than very small doses, acts as a poison, a hundred 
grains being sufficient to cause death. " When small pieces of perfectly clean 
camphor are allowed to fall upon the surface of pure water, they rotate and 
move about with great rapidity, sometimes for several hours together; but 
if while the camphor is rotating, the surface of the water be touched with 
any greasy substance (a glass rod dipped in turpentine answers best), all 
the floating particles quickly dart back, and are instantly deprived of all 
motion." This phenomenon appears to bo due to the continued escape of 
vapor from the surface of the camphor. 

776. Essential Oils containing S u 1 p h u r .— The oils ob- 
tained by distillation from black mustard-seed, from assafoetida, onions, horse - 



Questionb. — What precautions should always be observed in the use of these liquids? 
What is the reaction between turpentine and hydrochloric acid gas ? What are the uses 
of oil of turpentine ? What are other important oils of this class ? What are the princi- 
pal essential oils of the second class? What is common camphor? What are its proper- 
ties? What are examples of oils of the third class? 



AND RESINS. 465 

radisb, garlic, and hops, belong to this class. Many of them are character- 
ized by nauseous and offensive odors, which at the same time are remarkably 
persistent. The bad smell imparted to the breath by eating onions or garlic, 
for example, is occasioned by the continued presence of a minute quantity 
of the volatile oils of these vegetables in the air exhaled from the lungs. 

The volatile oils which are produced by the destructive distillation of 
vegetable and animal substances, are as a class called em^yreumatic. 

The essential oils are mainly used in the preparation of essences, perfumes, 
and cordials. The latter are generally made of brandy, flavored with various 
aromatic oils, and afterward sweetened. In the preparation of perfumery, a 
single oil or essence is rarely used by itself, but the best result is obtained by 
a skillful mixture of the odoriferous principles of many plants. Eau de Cologne, 
called the perfection of perfumery, owes its excellence to the application of 
this principle.* 

777. Fats . — F i x e d Oils . — The fixed oils are mostly destitute of either 
taste or smell ; but the presence of certain volatile acids imparts odors to somo 
of them : thus, butter contains butyri c acid ; goat's fat, an odorous acid called 
hyrcic acid_ ; while the nauseous smell of whale oil is due to the presence of 
an acid called phocenic aci^ . They do not evaporate in the air, are decom- 
posed by the action of heat, and are unctuous and greasy in their feeling. 
They dissolve readily in ether and in the essential oils, but are not soluble to 
any great extent in alcohol, and are entirely insoluble in water. All the oils 
have an attraction for oxygen, and when exposed to light and air, absorb it 
rapidly, and give out carbonin^ a cid and- hydrog en ; this action may be suffi- 
ciently energetic to produce ignition (spontaneous combustion), especially 
when tbe oil is distributed over porous substances, tow, cotton, etc. 



* " Odors resemble very much the notes of a musical instrument. Some blend easily 
and naturally with each other, and produce a harmonious impression, as it were, on the 
sense of smell. Heliotrope, vanilla, orange-blossoms, and the almond blend together in 
this way, and produce different degrees of nearly similar effect. The same is the case 
with citron, lemon, vervain, and orange-peel, only these produce a stronger impression, or 
belong, so to speak, to a higher octave of smells. And again, patchouly, sandal-wood, 
and vitivert form a third class. It requires, cf course, a nice or well-trained sense of 
smell to perceive this harmony of odors, and to detect the presence of a discordant note. 
But it is by the skillful admixture, in kind and quantity, of odors producing a similar im- 
pression, that the most delicate and unchangeable fragrances are manufactured. When 
perfumes which strike the same key of the olfactory nerve, are mixed together for hand- 
kerchief use, no idea of a different scent is awakened as the odor dies away ; but when 
they are not mixed upon this principle, perfumes are often spoken of as becoming sickly 
and faint, after they have been a short time in use. A change of odor of this kind is 
never perceived in genuine eau de Cologne. Oil of lemons, juniper, and rosemary aro 
among those which are mixed and blended together in this perfume. None of them can, 
however, be separately distinguished by the ordinary sense of smell ; but if a few drops 
of ammonia be added to their solution, the lemon smell usually becomes very distinct." 

Questions. — "What are their peculiarities ? "What are empyreumatic oils ? For what 
purposes are the essential oils chiefly used? What are cordials? In what does the per- 
fection of perfumery consist? What are the properties of the fats and fixed oils? To 
what are their odorp owing ? What is said of their attraction for oxygen ? 



456 ORGANIC CHEMISTRY. 

778. The fixed oils, according to the changes which they undergo through the 
absorption of oxygen, are divided into two classes, viz., the drim n ox siccative. 
oils, and the unctuous or greasy^ oils ; or those which become hard and resinous 
by exposure to the air, and those which remain soft and sticky under the 
same circumstances. 

779. Drying Oils . — L i n s e e d Oil, or the oil obtained by expres- 
sion from the seeds of the flax plant, is a representative of this class ; and is 
the oil generally used for mixing with paints, and in the manufacture of var- 
nishes. Its drying properties, which especially recommend it to the painter's 
use, are greatly increased by boiling it for some time, with the addition of a 
little litharge (protoxyd oOead) t As thus prepared, it is known as " boiled 
oil, v or linseed-oil varnish. Oiled silk is silk to which successive coats of puri- 
fied linseed oil have been applied. Glazier's putty is prepared by kneading 
together boiled linseed oil and pulverized chalk (whiting). 

The other principal drying oils are those extracted from rape-seed, poppy- 
seed, the seed of the castor : oil plant, and from walnuts. 

Printer's Ink is prepared by igniting linseed oil in suitable vessels, 
and allowing it to burn until it becomes thoroughly charred, and acquires a 
viscid consistency ; it is then mixed with a certain proportion of the finest 
varieties of lamp-black. 

780. Unctuous Oils . — This class includes the oils expressed from the 
fruit of the olive and the palm, and most of the oils and fats of animal origin. 
These oils, by exposure to the air, are liable to become sour and rancid, but 
they do not solidify. 

781. Composition of the Fats and Fixed Oils. — Most fats 
and fixed oils, vegetable and animal, are mixtures of two, and generally 
three, distinct compounds, each of which, taken singly, has all the properties 
of a fat or an oil. The first of these substances, called stearine (from crtap, 
tallow), is solid at common temperatures ; the second, pleine (from elaiov, oil), 
is liquid at common temperatures; the third, called margarine (from judpyapov, 
a pearl), on account of its pearly appearance, is also a solid at common tem- 
peratures. All the fats and fixed oils, therefore, may be regarded as mixtures 
of the fluid oleine with the solids stearine or margarine. If the solid be in 
larger proportion than the fluid, then the compound at ordinary temperatures 
is a solid, and resembles tallow or lard; if, on the contrary, the fluid consti- 
tuent prevails, the compound has the characters of an oil. For example, 
when olive oil is subjected to a cold of 40° JF., it deposits a solid fat, mar- 
garine, which may be separated by filtration and pressure ; the largest por- 
tion of the oil, however, consisting of cleine, retains its fluidity at a much 
lower temperature. Again, by subjecting mutton tallow to pressure, a per- 

Questions. — Into what two classes are the fixed oils divided ? What are drying oUs? 
"What are unctuous oils ? What is a type of the drying oils ? What is linseed oil ? For 
what is it principally used ? What is boiled oil ? What is oiled silk ? What is putty ? 
What are the other principal drying oils ? What is printers 1 ink ? What are included in 
the class of unctuous oils ? What is the composition of the fixed oils ? When will a fatty 
hody have the characters of a solid, and when of a liquid ? 



AND RESINS. 467 

manently fluid oil, oleine, is extracted, while the solid which remains has its 
melting point raised, and is much harder than the original tallow ; it consists 
of stearine and margarine, the latter of which melts at a much lower tempera- 
ture than the former. 

Stearine, margarine, and oleine are, however, susceptible of further analy- 
sis. They are, in fact, true salts, composed of an organic or fat acid, united 
to a base ; the acid being peculiar to each fatty principle, while the base with 
which it is naturally united, is almost always the same. The name given to 
this base is glycerine, and it is regarded as the hydrated oxyd of a radical, 
glyceryle. In stearine the existing acid is called stearic acid; in margarine, 
margaric acid; and in oleine, oleic acid. Stearine is accordingly the stearate 
of the oxyd of glyceryle, and margarine and oleine the margarates and oleates 
of the oxyd of glyceryle. Olive oil also must be described as a mixture of 
much oleate of the oxyd of glyceryle, and a little margarate of the same base. 

It may seem singular to the student that bodies of an acid character should 
exist in fats and oils. Such, however, is the case, and they exhibit acid 
properties in marked degree, such as reddening litmus paper, neutralizing 
alkalies, and uniting with bases to form salts. 

782. Soaps. — When fixed fatty or oily bodies are brought in contact 
with alkaline solutions at high temperatures, they undergo a change called 
s aponification ; that is to say, the strong alkaline bases (potash or soda) dis- 
place the weak base glycerine, and unite with the acids existing in the fats or 
oils to form a homogeneous mass, called soap. Soaps, therefore, are true salts, 
combinations of stearic, margaric, or oleic acid, with an alkaline base. 

Soaps are of two kinds, hard and soft. The former are made with soda 
alone, or a mixture of potash and soda, while the latter are made exclusively 
with potash. Soaps made with potash are soft, mainly by reason of the deli- 
quescent character of the potash, which is unable to harden in the presenco 
of any considerable quantity of water. A soda soap, on the contrary, may bo 
made to absorb more than its own weight of water without becoming fluid. 
Besides, in a potash soap, the glycerine, which, before saponification was com- 
bined with the fat acids, remains mechanically mixed with the soap, and pro- 
motes its fluidity. In the manufacture of so:la soaps, the soap is obtained 
in a nearly pure state by the addition of common salt to the watery solution 
in which the soap is suspended. Soap not being soluble in salt water, im- 
mediately separates from the water and the glycerine contained in it, and 
floats upon the surface, and in this condition may be removed, while the 
spent lye, glycerine, and salt are allowed to run to waste. When this treat- 
ment is applied to a potash soap, another change is occasioned which is 
purely chemical. The salts which the fatty acids form with potash are de- 
composed by^cl^ndejgf^od^urn^ and a mutual interchange of acids takes 

Questions. — What is the constitution of stearine, margarine, and oleine ? What is 
glycerine ? What are stearic, margaric, and oleic acids ? What is understood hy sapon- 
ification ? What is a soap? WheT are soaps hard or soft? Why are potash soaps soft ? 
How are soda soaps made hard ? What is the chemical composition of hard and soft soaps? 



468 ORGANIC CHEMISTRY. 

place ; and hence, when a potash soap is mixed with a solution 'of common 
salt, both the soap and the chloride of sodium are decomposed, and a soda soap, 
and chloride of potassium are formed. 

Hard soaps are generally made of tallow, and are mainly mixtures of stear- 
ate and margarate of soda ; soft soaps are, on the other hand, usually made of 
oils, soft Jats, and are mainly ole.ales.-of- potash, with glycerine mechanically 
mixed with them. Castile soap_ is manufactured of olive oil and soda, its 
mottled appearance being produced by the addition of oxyd of iron. Kesins 
form with the alkalies, salts, which possess characters allied to those of the 
soaps, and in the manufacture of common soaps, a quantity of resin (rosin) 
is mixed, on the ground of economy, with the fats. Such soaps have a yel- 
lowish appearance, and are known as yellow soaps. 

Soaps, by reason of their strong attraction for water, always retain a con- 
siderable quantity of it in their composition; the proportion in the best hard 
soaps varying from 25 to 30 per cent. It is possible, however, to prepare a 
solid soap containing more than its own weight of water. Such soaps look 
well when fresh, but contract greatly on drying. Dealers generally store 
their soap in cellars and damp places, since it is for their interest to sell as 
large a proportion of combined water as possible. 

Soap is freely soluble in pure water, but in salt water, and all other saline 
solutions, it is insoluble; soap made from the oil extracted from the cocoa-nut, 
is, however, an exception to this rule, as it dissolves freely in strong brine, 
and is hence much used as marine soap. 'When a solution of a soap having 
an alkaline base is mixed with a salt of any other base, double decomposition 
ensues, and an insoluble compound of the fatty acids with the earthy or me- 
tallic bases is precipitated. The salts of lime and magnesia contained in nat- 
ural waters act in this manner, and their presence in a water renders it hard 
and unfit for washing.* The slimy scum which is formed by the addition of 
soap to such water, is a compound of the fatty acids with lime or magnesia. 
The strong acids decompose both soap and fats, uniting to their bases, and 
setting free the fatty acids. 

Ammonia acts far more feebly upon fatty bodies than either pntfish or gnrl^ 

783. Cleansing Properties of Soaps. — The detergent, or 
cleansing action of soap depends entirely upon its alkaline constituents. 
The impurities upon the skin, or on articles of clothing, always contain a 
certain proportion of oily matter, which exuding from the pores of the sys- 

* The hardness of a water maybe easily tested by adding to it a few drops of a solution 
of soap in alcohol (tincture of soap). If the water remains clear, it is perfectly soft ; if it 
becomes cloudy, it may be regarded as hard — the degree of hardness being proportioned 
to the degree of cloudiness occasioned. 

Questions. — What is said of the use of resin in the manufacture of soaps ? What 
percentage of water is contained in soap ? Why will not soaps wash in salt water ? 
When a solution of an alkaline soap is brought in contact with an earthy or metallic base, 
what happens ? Why will not soaps wash in hard water ? What effect have acids upon 
soaps and fats ? What is the action of ammonia ? To what are the cleansing properties 
of soaps due ? 



AND RESINS. 469 

tem, and existing in the perspiration, acts as a cementing agent with what- 
ever dust or dirt is brought in contact with it. Water alone, by reason of 
its total want of affinity for all fatty or oily substances, is unable to dissolve 
these impurities, and effect their removal. An alkali, on the contrary, readily 
unites with the greasy and organic matter, and renders it soluble. 

When a soap is dissolved in water, a portion of its alkali is set free (by 
the substitution of water as a base), and uniting with the impurities intended 
to be removed, partially saponifies them, and renders them soluble or mis- 
cible with water. The fatty acids also, by their lubricity, cause the dissolved 
matter to wash away more easily. An alkali used alone would act more 
powerfully than any soap as a detergent, but it would tend to destroy the 
texture of the organic substance to which it was applied, and also to remove 
the colors of dyed fabrics. When used in the form of soap, its solvent powers 
are partially neutralized. In washing the surface of the body with soap, its 
alkaline constituent not only effects the removal of the dirt, but also dissolves 
off the cuticle, or outer layer of the skin itself, which being mainly composed 
of albumen, is soluble in alkaline solutions ; and thus every washing of the 
skin leaves a new and sensitive surface. 

"What are called washing fluids are merely solutions of the caustic alkalies. 
They facilitate washing simply by providing an excess of alkali. When the 
water emploj'-ed in washing is somewhat hard, their use in moderate quan- 
tity may be recommended, as they precipitate the earthy salts present in the 
water, and render it soft. An excess of free alkali, however, in washing 
always tends to injure fibers and occasion them to shrink. Camphene (recti- 
fied spirits of turpentine) is also employed to some extent in washing ; it 
acts as a solvent for grease, and its use is in no way injurious to fabrics. 

T84. Stearic Acid is a milk-white solid, inodorous, tasteless, and 
highly crystalline. Mixed with some marganc acid, it is extensively used 
for the manufacture of candles, which are sold under the name of stearine, 
or adamantine candles. It is obtained for this purpose mainly from tallow 
and lard, by heating them by steam in vats with a mixture of lime and water. 
Under these circumstances an insoluble lime soap is formed, while the gly- 
cerine remains dissolved in the water. This soap is then heated separately 
with dilute sulphuric acid, which unites with the lime to form an insoluble 
sulphate, and leaves the fat acids in a separate state floating upon the sur- 
face of the liquid. These, when cold, are submitted to pressure, by which 
the oleic acid is removed, and the stearic and margaric acids left in a nearly 
pure condition. Stearic acid melts at a temperature of 158° F. Margaric 
acid closely resembles stearic acid, but is more fusible, melting at a tempe- 
rature of about 140° F. Lard oil, extracted from lard by pressure, is nearly 
pure oleine. 

Questions. — Why will not pure water answer as a detergent ? How does a soap act in 
removing dirt ? Why do we not use alkalies alone as detergents ? What are washing 
fluids ? What is their use ? What is the appearance of stearic acid ? What are stearino 
candles ? How is stearic acid prepared ? What is said of margaric acid ? What is an 
example of nearly pure oleine ? 



470 ORGANIC CHEMISTRY. 

We apply the term lard to those animal fats which at common tempera- 
tures have a soft and unctuous consistency, and tallow to those which remain 
hard ; the only difference between the two is in the proportion of the constitu- 
ent, oleine, which is greater in lard than in tallow. The fats of carnivorous ani- 
mals and of birds are soft (lard), while that of ruminating animals is hard 
(tallow). Fish, or train oil is obtained from the blubber of whales, seals, 
and various fishes. Spermaceti is a peculiar fat found in cavities of the head 
of the sperm whale. It differs from other animal fats, inasmuch as it does 
not contain glycerine, but another basic substance termed ethal, while the 
fat acid combined with it is called ethalic acid. 

Olive oil, or the sweet oil of commerce, is obtained by pressure from the 
fruit of the olive-tree. It is composed chiefly of oleine and a little marga- 
rine. Palm oil, which within a comparatively few } r ears has become an im- 
portant article of commerce, is obtained principally on the West Coast of 
Africa, in immense quantities, from the fruit of a species of palm-tree. It 
has, when fresh, a deep orange-red tint, and an agreeable odor, and at ordi- 
nary temperatures has the consistency of butter. It consists of a fluid fat, 
oleine, and a crystallizable solid, resembling margarine, which has been called 
joalmatine, and which consists of palmatic acid and glycerine. 

Human fat contains palmatine, margarine, and some oleine.* 

784. Glycerine is a sweet, syrupy liquid, not volatile, and readily so- 
luble in water and alcohol. Until within the last few years its properties 
bave been overlooked, and it was not regarded as applicable to any useful 
purpose. In its solvent power, however, with respect to the metalloids, the 
salts, and the neutral organic bodies, it equals, if not surpasses, that of alco- 
hol or water. Exposed to the air, it does not become rancid, or readily 
dry up. It also possesses remarkable antiseptic properties, and preserves 
animal tissues immersed in it ia all their natural colors. It has recently 
been extensively applied in medicine for the dressing of wounds, burns, and 
sores, as a solvent for various medicinal principles in the place of alcohol or 
oils, and as a remedy for insect bites. It may be obtained in a nearly pure 
state by saponifying tallow with lime, and by various other processes. 

785. "When glycerine is strongly heated it is decomposed, and evolves a 
volatile, extremely pungent substance termed acroleine, which causes lachry- 
mation. The formation of this body occasions the disagreeable smell noticed 



* Bodies buried in churchyards, or submerged for a long time in water, are sometimes 
entirely converted into a peculiar substance resembling fat, termed adipocere. In the 
removal of the extensive cemetery, les Innocens, in Paris, in 1T67, more than 1509 bodies, 
■which had been interred in one pit, were found in this condition, and were to some extent 
disposed of to soap-boilers, and manufactured into Boap. 

Questions. — How does lard differ from tallow ? From what sources are lard and tal- 
low obtained ? From what sources is train oil obtained ? What is spermaceti ? What is 
olive oil? What is palm oil ? What are its constituents ? What does human fat consist 
of? What are the properties of glycerine ? What is said of its solvent powers ? What 
is acroleine ? 



AND RESINS. 471 

during the smoldering of a candle-wick, and it may be also perceived dur- 
ing the imperfect combustion of all kinds of fats. 

786. W a x . — The term wax is applied by chemists to substances derived 
from various sources, which resemble in composition and properties the wax 
forming the solid portion of honeycomb. It has long been a matter of dis- 
pute among naturalists, whether the bee merely collects the wax formed by 
plants, or secretes (manufactures) it from honey (sugar) in the tissues of it3 
body. The latter view of the case is now generally adopted. The constitu- 
ents of wax are the same as those of the fats and oils, viz., carbon, hydro- 
gen, and oxygen — the formula for bees-wax being C34II34O2. 

Bees- wax, in its natural state, is yellow, but is bleached white (white wax) 
by exposura in thin ribbons to the action of light, air, and moisture. It 
fuses at a temperature of 150°, and is soluble in ether and spirits of tur- 
pentine. When heated with boiling alcohol, it separates into different proxi- 
mate principles, myricine and cerine, the last of which separates from the 
alcohol on cooling in delicate needle-like crystals. It is doubtful whether 
these bodies are susceptible of saponification. Wax digested with oils, forms 
a kind of ointment termed cerates. "Wax also occurs in all plants, especially 
in the glossy coating or varnish observed upon the surface of leaves and the 
skins of fruit (as in the skin of the apple). From some species of plants it 
is obtained in sufficient quantities to constitute an article of commerce ; as 
the bayberry tallow, or myrica wax, which is obtained by steeping the leaves 
and fruit of a species of myrtle in hot water. The great demand for wax is 
for the manufacture of candles, which are first molded by the hand and then 
shaped by rolling upon a hard surface. "Wax burns with a beautiful clear 
light, and is the most expensive material employed for illumination. 

18 7. Resins . — Resinous substances are found in greater or less abun- 
dance in almost all plants, and are regarded as the products of the oxyda- 
tion of the essential oils. Many of them exude naturally from fissures or 
incisions in the bark or wood. They are all insoluble in water, but dissolve 
readily in alcohol, ether, and the essential oils. When pure and free from 
essential oils, they have no odor except when rubbed or heated. They are 
also good insulators of electricity, and become electric by friction. In color 
they are pale brown or red. 

788. Colophony . — Common pine resin (rosin), also termed colophony, 
which is the residue left after the distillation of crude turpentine, is a good 
example of this class of resins. It contains two distinct bodies having acid 
properties, called pinic and silvic acids> which may be separated from each 
other by treatment with alcohol. These acids unite with bases to form salts, 
and their combinations with the alkalies are true soaps (rosin soaps). Rosin 

Questions. — "What is wax ? "What is the origin of bees-wax ? Into what two principles 
may wax be divided ? How is white wax formed ? Under what circumstances is wax 
found in vegetables ? What is bayberry tallow ? What is said of the occurrence of resins ? 
"What are their general properties? "What is a characteristic example of this class of 
bodies ? How is rosin obtained ? What is its chemical name ? What is its composition ? 
What is pine oil ? 



472 ORGANIC CHEMISTRY. 

yields by distillation a great variety of products, the most important of which 
is a fixed oil, which is extensively used for lubrication and somewhat for 
illuminating purposes, under the name of sylvic, orpine oil. Rosin is extremely 
brittle, and may be easily reduced to a fine powder, in which condition it is 
used to increase friction, as it renders the surfaces to which it is applied 
rough and adhesive ; its application to the bows of violins, and to the 
cords of clock weights to prevent their slipping, are familiar illustrative ex- 
amples. Rosin ignited for a time and then extinguished, is converted into 
a soft, black, pitchy substance, generally known as ship's pitch, or shoemaker's 
wax. 

789. Lac . — This important resinous substance, which is exported from 
the East Indies to the extent of half a million of pounds annually, is pro- 
duced by the puncture of the bark of certain species of trees by an insect, 
and by its elaboration of the exuding juice into cells for its eggs. It occurs 
m commerce under three forms. Thus the broken off twigs of the trees 
incrusted with lac constitute stick lac, removed from the twigs it is seed lac, 
and when refined by melting and straining it is shellac. Stick lac, owing 
to the presence of the dead insect in its structure, yields by proper treatment 
a dye which is nearly, or quite as bright as that obtained from cochineal. 
Lac is also extensively employed in the preparation of varnishes, in the 
manufacture of hats (for stiffening the hat body), and as the principal ingre- 
dient in sealing-wax.* "What is called gold varnish is a solution of shellac 
in alcohol, colored yellow by gamboge and tumeric. 

Mastic, "Dragon's Mood," so called from its deep red color, and Sandarac, 
are also resins largely employed for the manufacture of varnishes. Copal 
is exceedingly hard, and of a light yellow color ; it differs from the other 
resins in being almost insoluble in alcohol and the essential oils. Copal var- 
nish is made by first fusing the resin, and then adding spirits of turpentine 
and linseed oil. Gum guiacum, much used in medicine, is the product of the 
lignum-vitse tree of the West Indies. 

190. Amber . — The source of amber was for a long time uncertain ; by 
some it was supposed to be a carbonaceous mineral, but it is now univer- 
sally considered to be a fossil vegetable resin, the product of a species of 
the pine family now extinct. Whenever found in its natural location in 
the earth, it is associated with carbonized wood or coal. It is chiefly found 
on the shores of the Baltic Sea, and is apparently washed out of the sand by 
the waves. The largest block known is in the Royal Museum of Berlin, 



* Common red sealing-wax is usually made of 4 parts of lac, 1 to 1A of Venice turpen- 
tine, and 3 parts of vermilion, the whole being fused together by a moderate heat. By 
substituting different coloring principles, different colored varieties of sealing-wax are 
prepared. 



Questions. — What is shoemaker's wax? "What is lac? What are its varieties ? What 
are its uses? What other resins are largely employed for varnishes ? What is said of 
copal ? What is amber ? Where is it principally found ? 



AND RESINS. 473 

aud weighs 13 lbs. Amber often contains insects so perfectly and delicately 
preserved, that they could not have become incorporated in the mass, ex- 
cept it was once in the condition of a volatile oil or a semi-fluid resin. It 
is the hardest of all the resins, has a yellowish color, and is slightly acted 
upon by alcohol or the essential oils. Being commonly translucent, and sus- 
ceptible of a fine polish, it is often made into ornaments, such as necklaces, 
the mouth-piece3 of pipes, etc. The beautiful black varnish used by coach- 
makers is a very carefully -prepared compound of amber, asphaltum, linseed 
oil, and turpentine. Amber is a compound of several resinous principles, and 
a peculiar acid called succinic acid. 

791. Balsams. — Many resinous substances, as they exude from trees 
or shrub3, are mixed with an essential oil, which either evaporates on com- 
ing in contact with the air, or is converted into resin by the absorption of 
oxygen. Such mixtures of resins and essential oils are called balsams. The 
crude turpentine or pitch which exudes from the pine is an example of a 
true balsam, since by distillation it is separated into a volatile oil — turpen- 
tine and hard resin. Among the other important commercial balsams are 
" Canada balsam,' 1 the product of the silver fir, " Venice turpentine, 11 the pro- 
duct of a species of larch, Copaiba balsam, balsam Tolu, Peru, and gum ben- 
zoin. The three former are merely natural varnishes, i. e., resins dissolved in 
volatile oils ; the latter contain in addition an acid principle. This acid in 
gum benzoin is called benzoic acid, and is chemically interesting by reason 
of the number and marked character of the salts which it forms with bases. 
Benzoic acid may also be obtained artificially as a product of the oxydation 
of the oil of bitter almonds. The gum itself is very fragrant, and is the chief 
ingredient in the incense burnt in Catholic churches. 

792. Gum Resins — This term is applied to a class of vegetable pro- 
ducts which contain in addition to a resin and an essential oil, a portion of 
gum and various other extractive matters. "When they first escape from in- 
cisions in the stems or branches of trees and shrubs, they are fluid and of a 
light color, but gradually harden, and become of a deeper hue. Most of 
them also possess a strong odor, and a warm, acrid taste. Owing to their 
mixed composition, they are not perfectly soluble in either water or abso- 
lute alcohol, but are completely dissolved by proof spirit. This class of 
substances includes many valuable medicinal principles, such as myrrh, asa- 
foetida, aloes, gamboge (the well-known coloring agent), scammony, and 
others. Opium is also included in this class. 

793. V a r a i s h is a solution of a resinous substance which is applied to 
the surface of bodies for the purpose of investing them with a hard, transpa- 
rent, lustrous coating. When the solvent for the resin is alcohol, the pro- 
duct is termed spirit varnish, and when an essential or drying oil, oil var- 



Questions. — What are its properties and uses ? What is said of its chemical composi- 
tion ? What are balsams ? What are examples ? What, is said of gum benzoin ? What 
are gum resins? What are their properties ? What are some of the principal bodies of 
this class ? What is varnish ? 



474 ORGANIC CHEMISTRY. 

nish. French polish is an alcoholic solution of shellac, with a little oil 
added. 

794. The Elastic Gums . — Two varieties of this class only are known 
in commerce — caoutchouc or India-rubber, and gutta percha. There are, 
however, several other vegetable products of a like character which have not 
been made practically available. 

Caoutchouc is obtained from the milky juice afforded by several species of 
tropical plants, in which it exists in the form of small globules suspended in 
an aqueous liquid, precisely in the same manner as the little globules of 
oily matter float about in milk. "When the juice is exposed to the air, the 
caoutchouc gradually separates, and hardens into a white elastic mass, inso- 
luble in water or alcohol. The usual black color of India-rubber is a discol- 
oration occasioned by the smoke of the fires over which the fresh product is 
dried. The addition of a little ammonia to the milky juice temporarily pre- 
vents the separation of the caoutchouc, and under these circumstances the 
caoutchouc may be exported in tightly-corked bottles in its natural condition. 
A short exposure to the air, however, soon occasions its separation as a 
milk-white solid. 

The physical properties of caoutchouc are well known. It is soluble in 
pure ether, naphtha, benzole, oil of turpentine, and the bi-sulphide of carbon. 
At a temperature a little above the boiling point of water it melts, but does 
not regain its solid, elastic state on cooling. Caoutchouc contains no oxygen, 
and is composed of carbon and hydrogen united probably in equal propor- 
tions. 

When caoutchouc is heated in connection with sulphur, it incorporates a 
quantity of the sulphur into its structure, and undergoes a remarkable change, 
becoming what is called vulcanized rubber. In this condition it is less liable 
to bo hardened by cold or softened by heat, and is also rendered more elas- 
tic and insoluble in ether and the essential oils. It is from this material that 
almost all India-rubber goods are now fabricated. Vulcanized rubber, by 
mixture with a proportion of bituminous or pitchy matter, and some earthy 
material like magnesia, may be converted into a hard, black, lustrous sub- 
stance, which works like ivory, and is extensively used for the manufacture 
of combs, pencil-cases, knife-handles, etc. 

Y lG 232 -A- s caoutchouc is unaffected by most chemical 

agents, and is at the same time supple and flexible, 
it admits of many useful applications in practical 
chemistry. Short flexible tubes for the connection 
of apparatus are easily formed by wrapping a piece of sheet rubber over a 
glass tube or rod (see Fig. 232), and cutting off the superfluous portions with 
a pair of scissors (see Fig. 233). On pressing together and gently warming 

Questions. — What substances are included in the class of elastic gums? From what 
Bourceia caoutchouc obtained? What is its natural condition and color? WTiat is said 
of its solubility ? What is its chemical composition ? What is vulcanized rubber ? 
What effect has the addition of 6ulphur upon the qualities of rubber ? 



NUTRITION AND GROWTH OF PLANTS. 475 




the fresh-cut edges, they cohere, and form a tube, 
which firmly tied at both ends, binds two separate 
glass tubes air-tight with each other. (See Fig. 
234) 

Most of the caoutchouc at present used is obtained 
from the country bordering on the banks of the 
Amazon, South America. 

195. Gutta Percha . — This substance, like 
caoutchouc, is obtained from the milky juice which 
exudes from several species of trees peculiar to 
Southern Asia. At ordinary temperatures it is 
slightly elastic and as tough and hard as wood ; but 
when immersed in warm water, it softens and be- 
comes highly plastic and ductile, regaining its original hardness on cooling. 
This property allows it to be molded with great facility into many articles of 
utility and ornament. Gutta percha possesses a dirty white color, and a pe- 
culiar leathery smell ; it is highly inflammable, and is insoluble in water or 
alcohol, but dissolves in ether, the essential oils, chloroform, and bi-sulphuret 
of carbon. 



Fig. 234. 



CHAPTER XXIY. 



THE NUTRITION AND GROWTH OF PLANTS. 



796. E lement s of Vegetable Organization. — The ele- 
ments which constitute the organic structure of plants are, as has been already 
stated, carbon, hydrogen, oxygen, and nitrogen — the three former being 
largely in excess. 

In addition to these, all plants contain various inorganic, or rather mineral 
substances, the presence of which in their structure is essential to a healthy 
growth and organization. The number and the nature of these mineral 
substances are ascertained by analysis of the ashes (the incombustible part) 
which plants yield by combustion. They are mainly potassa, soda, lime, mag- 
nesia, and sesquioxyd of iron, combined with carbonic acid, sulphuric acid, silicic 
acid, phosphoric acid, and various chlorides. The ashes of all cultivated plants 
contain these mineral substances ; but the proportions vary with the nature 
of the plant. Thus silica abounds in the stalks of grains and grasses, phos- 
phoric acid in the seeds of grain-bearing plants, potash in leaves and many 
edible roots, and lime in leguminous plants, peas, beans, etc. 



Questions. — What is gutta percha ? What are its properties ? What are the elements 
that make up the organic structure of plants ? What other substances are regarded as 
essential constituents ? How may we ascertain the nature of the mineral substances 
which enter into the composition of plants ? Do all plants contain the same mineral con- 
stituents ? Illustrate this. 



476 ORGANIC CHEMISTRY. 

The mineral constituents of plants do not necessarily exist in the living 
tissues in the same form as in the ashes afforded by the combustion of these 
tissues. Thus, sulphur and phosphorus appear to exist uncombined in albu- 
minous matter, while the earthy bases are very generally united iu the struc- 
ture of plants with vegetable acids. In the process of combustion, however, 
the latter become converted into carbonates, while the sulphur and the phos- 
phorus unite with oxygen to form acids, which m turn generally unite with 
one .of the bases present to form salts characteristic of these elements. 

797. Sources of Nutriment to P I a n t s .—Plants obtain their 
nutriment partially by their leaves and partly by their roots. The former are 
furnished with a great number of microscopic pores, or stomata* while in 
the latter the nutritious matter penetrates the cell-walls of the rootlets by 
the force of endosmosis. It must be, therefore, evident that the plant can 
only absorb its nutriment in a liquid or aeriform condition. 

198. The hydrogen and oxygen which plants contain are derived princi- 
pally from water which is absorbed as a liquid by the roots from the earth, 
or as vapor, from the air, by the leaves. The substances which make up the 
great bulk of the structure of all plants, viz., cellulose, lignine, starch, sugar, 
and gum, contain oxygen and hydrogen in exactly the same proportions as 
they exist in water, and they may in fact be regarded as merely compounds 
of carbon (their other constituent element) with water. The presence of 
water in a liquid condition in the plant is, moreover, indispensable to its de- 
velopment, since all the solid ingredients of plants are assimilated from the 
sap, which is rendered liquid by water. Plants, however, absorb through 
their roots much more water than is applied to the enlargement of their 
structure, and in such cases a constant evaporation takes place from their 
leaves. 

799. The carbon existing in plants is entirely derived from carbonic acid, 
carbon itself being insoluble in water. Plants absorb carbonic acid principally 
from the air through their leaves. Although but 2 measures of this gas are 
contained in 5,000 of air, its aggregate supply, by reason of the great extent 
of the atmosphere, is very large, and has been estimated to exceed seven 
tons for each acre of the earth's surface. The immensely-extended surface 
presented by the leaves of plants enables them to withdraw carbonic acid 
from the atmosphere in a very rapid manner. 



* In the leaf these pores are found mainly upon the under side. In the white lily, whero 
they are unusually large, and are easily seen by a simple microscope of moderate power, 
there are about 60,000 to the square inch on the epidermis of the lower surface of tho 
leaf, and only about 3,000 in the same space upon the upper surface. More commonly, 
there are few or none upon the upper side, direct sunshine being unfavorable to their 
operation. Their immense numbers make up for their n-inuteness. They are said to 
vary from less than 1,000 to 170,000 to the square inch of surface.— Gkay. 

Qr/ESTioxs. — Do they exist in the tissues in the same form as in the ashes of plants? 
Through what organs do plants obtain their nutriment? In what conditions is nutriment 
only absorbed by plants ? From what source do plants derive oxygen and hydrogen ? 
"What is said of the existence of water in plants? 



NUTRITION AND GROWTH OF PLANTS. 477 

Carbonic acid is also supplied to plants from the soil through their roots. 
Humus, in the course of its decomposition, continually evolves carbonic acid ; 
and the air in all soils rich in decaying vegetable matter always contains a 
much larger proportion of carbonic acid than an equal bulk of the general 
atmosphere. Carbonic acid does not, however, enter into and circulate in 
the structure of plants as a gas, but always in a state of solution. In the 
leaf the moisture with which the tissues are saturated becomes the medium 
of its absorption ; in the case of the root, it is taken up naturally in solution 
in water. Some chemists maintain that the soluble forms of humus (crenic 
and apocrenic acids) are directly absorbed by roots, and thus become sources 
of nutriment to the growing plant. This theory, from the fact that it .has 
been strenuously opposed by Liebig and other authorities, has not been gen- 
erally received, but the most recent investigations appear to substantiate its 
correctness. 

The carbonic acid absorbed by the plant, either by its leaves or roots, is 
decomposed ; its carbon constituent being retained and assimilated, while the 
oxygen originally combined with it is restored to the atmosphere. This de- 
composition takes place mainly in the leaves of plants, and is effected solely 
Under the influence of light. It goes on most actively when the plant is ex- 
posed to the direct action of the rays of the sun, but is entirely suspended 
during the night. It is also checked in a very marked degree during the 
daytime, when the light of the sun is intercepted by thick clouds. 

Plants, therefore, in the daytime continually absorb carbonic acid and exhale 
oxygen. 

In the night this process is to a degree reversed ; carbonic acid is absorbed 
as before, but the influence of light being withdrawn, it is again restored to 
the air unchanged. Oxygen, also, as the result of certain processes allied to 
oxydation, is at the same time abstracted to a very small extent from the at- 
mosphere. The action of oxygen under such circumstances is illustrated by 
the fact that the leaves of certain plants wdiich are bitter in the evening are 
sour in the morning, inasmuch as the products formed during the day become 
acid by oxydation at night ; when, however, the assimilation of carbon is 
recommenced under the influence of light, the excess of oxygen is neutral- 
ized, and the original bitter properties are restored. Furthermore, if during 
the night a plant be covered by a bell-glass, the atmosphere contained in it 
will be found to contain a larger amount of carbonic acid than before. This 
is occasioned by the oxygen of the air surrounding the plant effecting an 
oxydation on its surface, and thus producing a certain quantity of carbonic 
acid ; the amount, however, is very unequal in different plants, and is most 
abundantly produced by such as contain a large proportion cf easily oxyd- 
izable volatile oil in their glandular vessels. Flowers and fruits also form an 

Questions. — What is the source of carbon to plants in the soil ? In what condition 
does carbonic acid exist in plants ? What becomes of the carbonic acid absorbed by 
plants? Under what circumstances does its decomposition take place ? State the action 
of plants by day. What takes place at night ? How may the decomposition of carbonic 
acid be illustrated ? 



478 ORGANIC CHEMISTRY. 

exception to the usual action of vegetation, as they absorb oxygen from the 
atmosphere, and evolve carbonic acid.* 

The decomposition of carbonic acid by the green portions of plants may 
be easily demonstrated by placing fresh leaves in a bell glass partially filled 
with water, and partially with carbonic acid gas ; on exposing the glass to 
the sunshine, the carbonic acid disappears, and after some time is replaced 
by a rather smaller quantity of oxygen, which may be tested in the usual man- 
ner. 

The carbonic acid withdrawn from the air by the action of vegetation ia 
constantly reproduced and restored to the atmosphere by the respiration of 
animals, and by the processes of decay and combustion ; and these two classes 
of phenomena so completely compensate and balance each other, that the 
proportional quantity of ox} r gen and carbonic acid present in the atmosphere 
remains ever essentially unchanged. (§ 330.) 

800 It is the generally received opinion that plants derive their nitrogen 
entirely from the soil, by means of their roots, in the form of ammonia, al- 
though certain eminent French chemists maintain that this element is in part 
supplied directly from the atmosphere. The sources of supply of ammonia 
to soils are numerous ; it is absorbed and condensed from the atmosphere by 
dew, rain, and snow, and also by the clay and humus of the soil itself It 
is an abundant product of the decomposition of all nitrogenized animal and 
vegetable substances, and is undoubtedly produced to some extent by the 
direct contact of humus with the nitrogen of the air. 

In what manner the assimilation of ammonia takes place in the vegetablo 
kingdom is not certainly known. Its decomposition, however, furnishes 
plants with an additional source of hydrogen. The quantity of nitrogen con- 
tained in plants is comparatively small, and it is found chiefly in the sap and 
in the seeds. In 2,500 lbs. of hay there are 984 lbs. of carbon and only 32 
lbs. of nitrogen. 

801.- Plants derive their mineral, or earthy constituents from the soil, and 
the solution of these substances in water, which is necessary for their absorp- 
tion by root-fibers, is greatly facilitated by the action of carbonic acid. 
(§ 432). 

802. Soils owe their origin to the disintegration or gradual crumbling 
down of rocks, by the action of water, air, frost, and various other agencies. 
Through the action also of air, moisture, and carbonic acid, the stony parti- 



* There is a common belief that plants in flower at night deteriorate the air, and that, 
therefore, their presence in sleeping apartments is objectionable. The ill effects noticed, 
if actually occurring, are probably due, not to the formation of carbonic acid, but to the 
volatilization of certain volatile oils, many of which, in even very small quantities, act 
powerfully upon the animal system. 

Qtjestions. — How is the carbonic acid withdrawn from the air by plants restored ? 
From what source do plants obtain their nitrogen? Do plants absorb nitrogen directly 
from the atmosphere ? From what source do plants derive their mineral constituents ? 
What is the origin of soils ? Through what agency are certain of the mineral constituents 
of a soil rendered soluble ? 



NUTRITION AND GROWTH OF TLANTS. 479 

cles which make up a soil are chemically decomposed, and certain of their min- 
eral constituents, potash, soda, etc., are rendered soluble and capable of assimi- 
lation by plants. The most abundant constituent of soils is silica (sand\ 
which frequently forms nine tenths of their entire weight. Good arable land, 
however, always contains a large proportion of alumina (clay), and in soils 
underlayed by limestone or calcareous rocks, the proportion of carbonate cf 
lime present is often very considerable. 

The relative proportions of sand, clay, and lime in soils give to them cer- 
tain peculiar physical characters. A soil in which sand predominates is light 
and porous ; an excess of clay, on the other hand, renders it heavy and re- 
tentive of moisture. The best soils are those in which the earthy constitu- 
ents are so proportioned that the light, porous qualities of one are balanced 
by the close, retentive properties of the other. 

The quantity of organic matter (humus) derived from the decomposition of 
animal or vegetable substances present in a soil, essentially modifies its char- 
acter. The average amount of organic matter contained in soils is about 5 
per cent. Fertile alluvial soils, or those deposited from water, are generally 
characterized by the presence of a much larger proportion, and in some peaty 
soils, the amount may exceed ^0 or 80 per cent. 

803. Although plants obtain a large proportion of their nutriment from 
the air, yet as they abstract from the soil considerable quantities of earthy 
matter, which is only replaced naturally by the slow disintegration of min- 
eral substances, it is evident that the long-continued cultivation of the same 
plant upon the same soil may so far exhaust its soluble mineral constituents 
as to render it unfruitful. This is especially the case where large crops are 
raised year after year, and entirely removed from the soil to furnish food for 
men and animals. As different plants, however, require for their nourishment 
different mineral substances, or different quantities of the same substance, a 
soil which has become unfitted for the growth of one plant, may still contain 
the elements necessary for the support of another ; and hence a succession of 
crops of different vegetables may be raised upon the same soil, when two 
successive crops of the same vegetable could scarcely be obtained. This sys- 
tem of cultivating different plants in succession, upon the same soil, is termed 
the rotation of crops, and the period of time over which the rotation is al- 
lowed to extend is usually several years. During the interval which, under 
these circumstances, elapses between two successive crops of the same na- 
ture, the soil has time to renew itself; or in other words, it regains through 
the gradual decomposition of its insoluble, stony compounds, the constituents 
originally abstracted from it. In England, wheat is ordinarily grown upon 
the same soil only once in four or five years, the intermediate crops being 



Questions. — What is the most abundant constituent of soils? What influence has an 
excess of sand upon a soil ? What clay ? What is the composition of the best soils ? 
What is the average quantity of organic matter in soils? How does the growth of plants 
tend to impoverish a soil ? What is understood by the rotation of crops ? HW does the 
system of rotation tend to benefit a soil ? 



480 ORGANIC CHEMISTRY. 

turnips, barley, oats, and potatoes, crops which require but a small quantity 
of the mineral constituents which are essential to the growth of wheat. 

The resuscitation of an exhausted soil is also often effected by allowing it 
to fallow, or remain without a crop, exposing it at the same time (by plow- 
ing) to the action of air and moisture. 

804. Manures . — The method, however, of obtaining from the soil "the 
largest produce, consists in presenting to the plants cultivated upon it all the 
materials requisite for their nutrition in sufficient quantity, and in the condi- 
tion w r hich will most readily admit of their absorption. This is accomplished 
through the agency of manures. 

The most valuable and energetic of all manures are the excrements of 
men and animals, inasmuch as they are capable of yielding to the soil, through 
their decomposition, a large quantity of ammonia and carbonic acid, and the 
principal mineral substances which enter into the composition of plants. By 
acting as ferments, they also assist in rendering useful, materials which with- 
out them would be far less beneficial. The flesh and blood of dead animals, 
fat and oily matters, hair, wool, skin, horns, hoofs, and bones, are also highly 
efficacious as manures. Guano, which is the decomposing excrement of sea- 
birds, owes its value principally to the ammonia and phosphate of lime which 
it is capable of yielding to plants. These two ingredients, in the best varieties 
of guano, constitute about one third of its entire weight. Animal substances 
which decompose most readily, such as excrement, blood, flesh, etc., yield am- 
monia and carbonic acid most rapidly, and constitute the most powerful 
manures; those, on the contrary, which decompose more slowly, are less 
powerful, but more lasting in their effects. 

Animal manures exposed to air are liable to deterioration by the volatiliza- 
tion and escape of their ammonia. They may also, when incorporated with 
the soil, prove injurious by evolving a greater quantity of ammonia and car- 
bonic acid than plants require or can absorb. Agriculturalists express this 
when they speak of a manure as being too strong. These evils may be in a 
great measure prevented by incorporating with the strong manure a consid- 
erable quantity of vegetable refuse, straw, weeds, leaves, peat, etc., which 
substances, being less prone to decomposition, check the otherwise too rapid 
putrefaction. The animal products at the same time react upon the vege- 
table substances, and gradually bring them into such a state as renders them 
also most valuable additions to the soil. Common farm-yard manure is an 
example of a mixture of this character. The loss of ammonia may also bo 
effectually prevented by adding to manures a small quantity of a weak solu- 
tion of any acid, or gypsum (sulphate of lime), or copperas (sulphate of iron). 



Questions. — What is fallowing? In what manner can the largest produce be obtatned 
from the soil '? What are the most valuable of manures ? Why are animal manures es- 
pecially valuable ? What is guano ? To what does it mainly owe its value as a manure ? 
What is said of the comparative effect of different animal manures? Under what circum- 
stances will animal manures deteriorate ? When are they said to be too " strong ?" How 
may these evils be obviated ? 



NUTRITION AND GROWTH OF PLANTS. 481 

805. Vegetable manures, under which head are included vegetable refuse 
of all kinds, straw, leaves, sea-weed, and green crops which are merely sown 
to be plowed in, yield by their decomposition, when mixed with the soil, 
carbonic acid and small quantities of ammonia and the mineral constituents 
of plants. They also render a soil porous and retentive of moisture and am- 
monia. They are most a Ivantageously used when employed in combination 
with some kind of animal manure. 

806. Mineral manures are generally used for specific purposes. Of these 
the most important is lime. This substance acts mechanically by giving a 
proper consistency to soils, and chemically, by facilitating the decomposition 
and promoting the solubility of the more insoluble mineral and vegetable com- 
pounds. Quicklime is especially useful in soils rich in humus — peaty or mossy 
soils. Soils of this kind generally contain an excess of acid, which greatly 
interferes with their fertility ; this acid is neutralized by the addition of hme. 
Quicklime, however, should never be mixed with animal manures, as it tends 
to promote the escape of ammonia. Gypsum, or marl which contains lime 
in combination, may be used in such cases with beneficial results. Wood 
ashes act upon soils and manures in the same manner as lime , they are, 
however, more valuable than lime, as they contain alkaline salts and phos- 
phoric acid. Hard coal ashes have but little value as manures ; they do not 
contain any appreciable quantity of alkaline salts or phosphoric acid, and 
consist mainly of silica, alumina, oxyd of iron, and a small percentage of 
sulphate of lime. Phosphate of lime is an exceedingly valuable manure, and 
as it is found in almost all plants, it may be applied with advantage to almost 
all cultivated soils. It exists abundantly in bones and in guano, and in 
smaller quantity in all organic manures and in the ashes of plants. Phos- 
phate of lime is the special mineral constituent of wheat, and its presence in a 
soluble condition in a soil, is necessary for the successful cultivation of this 
cereal. Gypsum or sulphate of lime is a valuable addition to soils which do 
not contain it. It is partially useful as supplying lime and sulphuric acid, 
and partially as an agent for fixing ammonia. It is especially adapted for 
clover, bean, and pea crops. 

A thorough tillage, or a complete pulverization and separation of the par- 
ticles of a soil, will go far toward compensating for a lack of manures. "With 
every increase in the comminution of the particles of a soil, an increased 
power is given to the soil for the absorption, retention, and condensation of 
moisture, ammonia, and carbonic acid, an opportunity for the free permeation 
of atmospheric air, a facility to the rootlets of plants for extension, and a 
consequent increased facility for receiving and appropriating nourishment. 
This fact is strikingly illustrated by a comparison of the sterile soils of New 

Questions. — What is the action of vegetable manures ? How may they he most advan- 
tageously used ? What is said of lime as a manure ? Upon what soils is the use of lime 
especially beneficial ? When should lime not be used ? What is said of the fertilizing 
action of wood ashes? What of hard coal ashes ? What of phosphate of lime? What 
of gypsum ? What is paid of the importance of thorough tillage and pulverization of a 
eoil ? Ilow is this illustrated ? 

21 



482 ORGANIC CHEMISTRY. 

England and the fertile ones of the "West. Both have been formed from the 
disintegration of the same varieties of rocks, and both contain the same min- 
eral constituents in nearly the same proportion. In the former, however, the 
mineral particles are extremely coarse, but in the latter they are nearly in the 
state of an impalpable powder. The fertile soils of the West also contain a 
large percentage of humus in an advanced stage of decomposition, while very 
often the humus in the soils of New England is in a state allied to charcoal, 
and completely insoluble. 



CHAPTER XXY. 

ANIMAL ORGANIZATION AND PRODUCTS. 

80 T. Animal Organization . — Inasmuch as all animals derive their 
sustenance, either directly or indirectly, from the vegetable kingdom, the ele- 
ments which enter into their composition are essentially the same as those 
contained in plants. Most animal substances are, however, more complex 
in their nature than substances of vegetable origin, and as a necessary 
consequence, they are less permanent, and the products of their decomposition 
are more numerous. Water and fat are almost the only substances which 
contain but two or three elements that exist in the animal organism — almost 
all the others being also rich in nitrogen, sulphur, and phosphorus. 

808. Proximate Animal Constituents . — The chief proximate 
constituents that are found in the animal system are albumen, fibrine, caseine, 
gelatine, fat, water, and phosphate of lime. The proportions of solids and 
fluids in the animal body are very unequal. A man of 154 lbs. weight con- 
tains 116 lbs. of water, and only 38 lbs. of dry matter. By slow desiccation 
this water may be got rid of, when the body will assume the condition pre- 
sented by the mummies of Egypt and Peru. The fluids of the body, as they 
exist in the living tissues, are not simply water, but watery solutions of va- 
rious organic and inorganic substances. 

Of the proximate animal constituents named above, albumen, fibrine, and 
caseine appear to have essentially the same composition and properties as 
the substances of the same name originating in vegetable tissues. The two 
first are diffused throughout the whole body ; the third is found only as a 
special secretion. 

809. Albumen . — The best example of animal albumen is to be found 
in the white of an egg. This, when evaporated to dryness, yields about one 

Qtjestions. — What are the elements of animal substances ? In what respects do animal 
substances differ from vegetable ? What are the chief proximate constituents of the ani- 
mal system What is the relation between the solids and the fluids in the animal body ? 
What is said of the composition and distribution of animal albumen, fibrine, and caseine ? 
What is the best example of animal albumen ? 




ANIMAL ORGANIZATION AND PRODUCTS. 483 

eighth of solid albumen, the rest being water. The ashes of albumen thus 
obtained contain common salt, carbonate, phosphate and sulphate of soda, and 
phosphate of lime, which saline substances constitute about 5 per cent, of the 
weight of the white of the egg, or 1$ per cent, of the weight of the dried albu- 
men. The yolk of eggs consist essentially of albumen, holding in suspension 
drops of yellow oil. This oil forms about two thirds of the weight of the 
yolk in a dried state, and may be extracted from the coagulated yolk by 
pressure, or by digestion in alcohol. 

"When albumen is agitated with water, little solid bodies are formed, which 
under the microscope resemble the cells which make up the cellular tissue of 
animals, and are perhaps the nearest approach to an organic structure that 
man has yet been able to produce artificially. 

810. F i b r i n e is found in the animal body in two distinct states, viz., in 
a solid condition in muscular flesh, and as a fluid in the blood. A piece of 
lean beef washed in cold water until it is perfectly white, affords us an ex- 
ample of fibrine in the first condition, associated with membraneous matter, 
nerves, fat, etc. It may be extracted from the blood in a purer condition, 
by strongly agitating that fluid, in its recent and warm state, with a bundle 
of twigs. The fibrine adheres to these latter in the form of long, elastic 
strings, and is removed and cleansed by washing with cold water. In this 
condition it contains only a little fat, p IG _ 237. 

which may be extracted by ether. 

The lean part of the muscles of all 
animals consists chiefly of fibrine, and 
it is, therefore, the principal constituent 
of animal flesh. Fig. 235 represents 
the structure of muscle as seen under 
the microscope, the cross wrinkles 
showing the way in which the fibers contract in the living animal. Fibrine 
derives its name from its peculiar fibrous appearance, but under the micro- 
scope it appears to be composed of small globules arranged in strings. When 
pure, it is quite tasteless, and insoluble both in hot and cold water, but by 
long-continued boiling it is partially dissolved. By drying it shrinks pro 
digiously in volume, loses about 80 per cent, of water, and becomes transpa- 
rent and horny, and in this condition may be preserved for an indefinite pe- 
riod. Fibrine, when in solution, assumes the solid form spontaneously, as 
as soon as it is withdrawn from the influence of life. It is this which 
causes blood to coagulate almost as soon as it is drawn from the veins — the 
coagulation being a net-work of fine fibers of fibrine inclosing the liquid se- 



Questions.— Of what does the white of an egg consist ? What is the composition of the 
yolk ? What phenomenon of alhumen is mentioned ? In what conditions is fibrine found 
in the animal economy ? How may it be prepared in a state approaching to purity? Of 
what part of the animal system does it form the principal part ? What is the origin of its 
name? What are its properties ? What is said of fibrine in solution ? What causes the 
coagulation of the blood ? 




484 ORGANIC CHEMISTRY. 

rum and coloring principle of the blood. Owing to this circumstance, little 
or nothing is known of tibrine in the soluble state, but it is believed that the 
chemical composition of soluble and insoluble fibrine is somewhat different. 
Its composition is represented by the formula C400H310N50O120PS. 

811. Ca s e i ne in the animal system occurs only in milk. Its composi- 
tion and properties have been already described. (§ 706.) 

812. Gelatine . — Various parts of the animal body, particularly the skin, 
the tendons, cartilage, and the soft portions of the bones, dissolve completely 
by long boiling in water, and produce a liquid which solidifies on cooling to a 
jelly. The substance so produced is termed gelatine. Chemists do not regard 
it as existing naturally in the system, inasmuch as it is never found in the 
fluids of the body, as might be expected from its ready solubility in warm 
water ; but it is supposed to be produced by a specific chemical change of 
some of the albuminous principles by the action of the hot water and the 
oxygen derived from the air. The gelatine extracted from cartilage appears 
to differ somewhat from that extracted from animal membranes proper, 
and has received the distinctive name of chondrine^ The term cartilage is ap- 
plied to a dry, elastic tissue, very widely distributed in the animal economy, 
which sometimes serves to connect the ends of bones which move upon each 
other, and sometimes constitutes prolongations of the bones themselves, as for 
example, in the ribs, thus increasing their elasticity. 

Gelatine is an important constituent of the animal body, and is obtained from 
almost all solid parts of it, but more especially from the tendons, ligaments, 
the inner skin, and from bones and horns. It is very rich in nitrogen, and 
contains some sulphur, but it is not allied to the proteine group of substances. 
Its formula is C13H10N2O5S. Gelatine is exclusively an animal product, and 
is never found in plants, pectine being the vegetable jelly principle. 

Common glue is dried gelatine, and is prepared by boiling refuse skin and 
bones, and evaporating the solution. The liquor yields on cooling a thick 
jelly, which is cut by wires into thin layers, and dried by exposure to the 
air. Isinglass, which is the purest variety of gelatine, is the dried swimming, 
or air-bladder of several varieties of fish, especially of the sturgeon. Gelatine 
is also extracted from the tender and ligamentous part of calves' feet, for the 
purpose of forming the well known "calves' foot jelly." 

A dilute solution of gelatine prepared from clippings of hides constitutes 
the size which is usually applied to paper to fill up its pores, and thus pre- 
vent the spreading of ink. The difference between writing and printing paper 
consists simply in the fact, that the former is sized, while the latter is not.* 

* A cheaper kind of sizing for paper is also prepared by boiling resin with a strong so- 
lution of potash. This is first added to the paper pulp, and when it has become thor- 
oughly incorporated, a solution of alum is poured in. The alumina displaces the potash 
in combination with the resin, and forms a more insoluble compound in the fibers of the 
paper. 

Questions. — What is said of caseine? How is gelatine prepared ? What is gelatine? 
What is said of the distribution and composition of chondrine ? What is cartilage ? What 
is glue ? What is isinglass ? What is size ? For what purpose is size applied to paper ? 



ANIMAL ORGANIZATION AND PRODUCTS. 485 

^Gelatine is largely employed as an article of food, in soups, jellies, etc., but 
it possesses very little nutritive value. In an indirect way, under the condi- 
tions of a restricted diet usually met with in a sick room, its administration 
in the form of jellies, etc., appears to be beneficial, as it seems to protect some 
of the constituents of the body from waste. 

Gelatine united with tannic and gallic acids produces insoluble com- 
pounds, and the application of this principle to the manufacture of leather 
has been already noticed. Skins may, however, be converted into leather by 
other methods; as by impregnating them, after they have been freed from 
fatty matters by digestion in alkalies, with a solution of common salt and 
alum, and then working them with various oils. Glove leather is prepared 
in this manner ; the still softer chamois, or wash-leather is obtained by work- 
ing the skins for a long time with the brains of certain animals or the yolks 
of eggs — the effect in both instances being due to the action of certain pecu- 
liar oily or fatty substances. 

813. G 1 y c o c o 1 1 . — By boiling gelatine with dilute sulphuric acid, and 
afterward separating the acid by chalk, a very remarkable change is effected — 
the gelatine being converted into a sweet, crystallizable substance, which is 
termed glycocoll, or sugar of gelatine. 

814. Brain and Nerves . — The substance of the brain, nerves, and 
spinal marrow differs from that of all the other animal textures. It appears 
to be albumen in a peculiar state, associated with certain remarkable fatty 
substances, and in the brain especially a large amount of unoxydized phos- 
phorus is believed to be present. Only about one fifth part of the nervous 
tissue, however, is solid matter. The phosphorus contained in the brain is 
said to amount to 3 or 4 per cent, of its entire weight. 

815. The Skin of animals consists of two layers, the skin proper, called 
also the cutis, and the derma, which envelopes the muscles and the bones ; 
and the outer layer, the epidermis, or cuticle, which originates from the for- 
mer, and consists mainly of albuminous cells, which losing their liquid con- 
tents by evaporation, gradually become flattened scales at the surface. These 
undergo constant exuviation, and are constantly replaced from beneath, the 
superficial ones becoming dry and horny (scarf skin), and serving as a pro- 
tection to the sensitive or true skin underneath. The lowest portion of. 
the cuticle, resting on the cutis, is called the rete mucosum, and contains the 
pigment which in the dark races imparts color to the skin. This pigment 
seems to be produced by the agency of sun-light and continued high tem- 
perature, and contains a large percentage of carbon. 

The cuticle, or outer skin of most animals is perforated by numerous small 
orifices, through some of which hairs pass, while others give passage to the 
fluids of perspiration, or allow certain oily fluids to exude. " In the human 

Questions. — What is the nutritive value of gelatine ? How is leather formed other 
than hy tanning ? What is glycocoll ? What is said of the composition of the Drain and 
nerves? Of what does the skin consist? How is the epidermis formed? What ia the 
rete mucosum ? What is said of the pores of the skin ? 



486 



ORGANIC CHEMISTRY. 



Fig. 236. 



system the pores are more numerous in some parts of the body than in others, 
but the outer skin of a full-grown man is sprinkled over with about seven 
millions of them, while the united length of certain spiral vessels connected 
with them is reckoned at 28 miles." Through the pores of the skin, also, 

air enters and escapes continually in 
a healthy state of the body, as it does 
from the air-vessels of the lungs. 

Pig. 236 represents a vertical sec- 
tion of the skin greatly magnified, a 
being the cuticle, or outer skin, b d 
the true skin, e the sweat glands and 
their ducts, the outlets at. the surface 
being pores, / hairs, g cellular tissue. 
816. Horny Matter. — Hair, 
wool, bristles, feathers, nails, claws, 
and hoofs of animals are regarded as 
having the same general chemical 
composition as that of the epidermis, 
of which they may be considered as 
appendages. They are insoluble in 
water, but soften in boiling water, 
and entirely dissolve by continued 
digestion in caustic alkalies. They 
contain several oily or fatty sub- 
stances, generally colored, from which 
they derive their peculiar hue. 

Each hair originates in a little flask-shaped follicle (f Fig. 236), which is 
formed by a depression of the cutis, and lined by a continuation of the cuticle. 
The hair grows by constant prolongation from this follicle, and its color is 
due to a peculiar colored oil, which in black hair contains a considerable quan- 
tity of iron. The surface of the hair is scaly, and not smooth, as it appears 
to the naked eye ; and in the case of wool, which is a modification of hair, 
the edges of the fiber, seen under a microscope, have the appearance of a 
fine saw, with the teeth sloping in a direction from the roots to the points. 
"Were a number of thimbles with uneven edges inserted into each other, a 
cylinder would result not dissimilar in outline from a filament of merino 
wool, the appearance of which, under the microscope, is represented by Tig. 
237. This peculiar structure of wool gives it the property of felting, so that 
when a mass of wool is alternately compressed and relaxed, the little imbri- 
cations or scales of the fibers lay hold of and match into each other, and thus 
compact the whole into a solid tissue, or fell. Some varieties of hair, included 
under the term fur, have also sufficiently roughened surfaces to enable them 




Questions. — What is said of the composition of hair, horns, etc. ? What of the origin 
of hair ? To what does hair owe its color ? What is the external structure of hair ? 
Why does wool felt ? 



ANIMAL ORGANIZATION AND PRODUCTS. 487 





to felt. Fig. 238 exhibits the appearance of the hair of the seal (a) and of a 
species of caterpiller (b), YiG. 238. 

■^*tll ~. when viewed under the 

fe§HS 1 tfj& microscope. -■/ — 

817. Bones.— Jho 
bones of animals arc 
composed of organic 
matter, which is essen- 
tially the same as car- w;\ 
tilage, and of earthy 
matter, consisting chief- 
ly of phosphate and 
carbonate of lime — the 
latter constituting in 
mammalia about two 
thirds of the weight of the bone.* The organic 
and earthy bases contained in bones may be easily separated from each other. 
Thus when a bone is digested for some days in a dilute solution of hydro- 
chloric acid, the earthy salts dissolve out, leaving the cartilage soft and flexi- 
ble, but retaining exactly the shape of the bone. To accomplish this per- 
fectly, it is necessary to renew the liquor several times, and finally to wash 
the cartilage with fresh water until no trace of acid remains. The cartilage 
may also be removed by heating the bone for some time in an open fire with 
free access of air — the organic matter in this way being burned away, while 
the bone-earth remains. 

The bones of mammalia and of birds agree very closely in chemical com- 
position, but the bones of fishes vary considerably as regards the relative pro- 
portions of contained earthy and organic matter. In what are called the 
cartilaginous Jlshes, sharks, etc., the bones are almost entirely destitute of 
calor.reous salts, and in the bones of all fishes the proportion of cartilaginous 
ma#er is always greater than in those of other vertebrated animals; hence 
tb j ..exibility of the bodies of fishes. The composition of fish-scales resembles 
that- of bone, since they contain from 40 to 50 per cent, of phosphate of lime, 
from 3 to 10 per cent, of carbonate of lime, and from 40 to 55 per cent, of 
organic matter. 

* The folio-wing is an average composition of the bones of a healthy adult man : — 

Cartilage 32*17 

Blood vessels 1-13 

Phosphate of lime 51-04 

Carbonate of lime 11 "30 

Fluoride of calcium 2*00 

Phosphate of magnesia 1-16 

Soda, chloride of sodium 1-20 

100 -00 



Qttestions. — What is the composition of bones ? How may the constituents of bones bo 
1 ? How do the bones of mammalia^ birds, and fishes correspond ? 



488 ORGANIC CHEMISTRY. 

818. Th e Teeth have essentially the same composition as the bones, 
except that they contain less cartilage. The white external part of the tooth 
beyond the gum, called the enamel, is almost wholly composed of phosphate 
of lime, carbonate of lime, and a small quantity of fluoride of calcium, and 
contains only a trace of animal matter. 

819. Shells are composed of a mixture of carbonate and phosphate of 
lime. The shells of Crustacea, lobsters, crabs, etc., usually contain from 50 
to 60 per cent, of carbonate of lime, from 4 to 5 per cent, of phosphate, and 
the balance animal matter. The shells of mollusca, oysters, clams, etc., on 
the contrary, are nearly pure carbonate of lime, and contain scarcely any 
phosphates or organic matter. 

820. Milk. — This peculiar liquid is secreted by the female of the class 
mammalia for the support of its young, and seems to contain the same con- 
stituents, although in somewhat different proportions, in ' all the different 
species of animals producing it. Milk is wonderfully adapted for the office 
it is naturally intended to discharge, viz., that of providing materials for the 
rapid growth and development of the young mammalian animal ; inasmuch 
as it contains caseine, a nitrogenous matter nearly identical in composition 
with muscular flesh, fat, sugar, and various salts, the most important constitu- 
ent of the latter being phosphate of lime. This last is held in complete solu- 
tion in the slightly alkaline liquid, and sustains an important relation to the 
formation and growth of bone. The following analysis exhibits the com- 
position of 1,000 parts of cow's milk in a fresh state : 

Water 873-00 

Caseine 48*20 

Fat (butter) 30-00 

Milk sugar 43-90 

Phosphate of lime, magnesia, and iron 2*80 

Chlorides of potassium and sodium, with a little free 

soda in combination with caseine 2-10 

1,000 

"Woman's milk contains more sugar, but less caseine and butter than the 
milk of the cow. The latter is not so well adapted to the functional wants 
of the child, but may be improved by diluting it with water and sweetening 
it with sugar, the effect of which is to reduce the percentage of the nitrogen- 
iz3d element, the caseine, and render it more suitable for digestion and assimi- 
lation. " Milk, moreover, is not suitable as the sole nourishment of adult 
life, since it does not contain in sufficient quantity those phosphorized com- 
pounds which are necessary to repair the waste of the tissues, which at this 
period are more active than in infancy." 

"When milk is viewed under a microscope of moderate power, it is seen to 
consist of a perfectly transparent liquid, in which are suspended numerous 



Qttestions. — "What is the composition of the teeth ? Of shells? "What is milk? What 
is its natural office ? What is its general composition? In what respect does woman's 
milk differ from cow's ? What is the appearance of milk under the microscope ? 




ANIMAL ORGANIZATION AND PRODUCTS. 489 

globules of fat, as is represented in Fig. Fig. 239. 

239. These globules are the butter, and 
mainly give to milk its opaque, white 
appearance. When milk is allowed to 
stand, the globules, by virtue of their 
low specific gravity, rise to the surface, 
and form a layer of cream, and by strong 
agitation or churning, they may be fur- 
ther made to coalesce into a mass, and 
form "butter." It is also believed that 
each fat globule is inclosed in a little sack 
of caseine, which is ruptured by the agita- 
tion. During the operation of churning, 
oxygen is absorbed from the air, the 
temperature rises, and the milk, if not already acid, turns sour. 

Butter consists of a mixture of margarine, oleine, and a peculiar volatile, 
odoriferous principle termed butyrine, which contains butyric acid. In order 
that butter should keep well, it is necessary that the buttermilk should be 
thoroughly freed from it, since the caseine and albumen contained in this 
readily undergo decomposition, and produce an acid fermentation which sep- 
arates the butyric acid and other volatile acids, and imparts to the butter a 
disagreeable, rancid taste. This same object, i. e., the preservation of butter, 
can be also attained by melting the butter, when the watery part subsides 
and carries with it the azotized matter. The flavor of the butter is, however, 
somewhat impaired by this process. 

821. Milk, when in a fresh state, is always feebly alkaline ; but it soon 
sours in the air, particularly in warm weather — lactic acid being developed. 
The presence of this acid causes the caseine to coagulate, or become inso- 
luble, when it separates in clots, carrying the fatty globules with it. Milk in 
this condition is said to be turned. This change may be prevented, without 
injuring the quality of the milk, by the addition of a minute quantity of car- 
bonate of soda. 

822. Cheese is a mixture, in various proportions, of coagulated caseine 
and butter. The caseous matter is separated in the form of cheese, by leav- 
ing the milk for some little time at a temperature of 120° F. in contact with 
a piece of the lining membrane of the stomach of a calf, which is called ren- 
net. This by its presence is believed to cause a sort of acid fermentation, 
which causes the milk to separate into a solid white opaque curd, and a thin, 
translucent whey, the former consisting chiefly of caseine and butter, and the 
latter of water, holding in solution most of the saline constituents of the 
milk, together with the milk sugar. The coagulum thus obtained is sepa- 

Qttestions. — In what condition does butter exist in milk ? How is butter collected in 
a separate state ? What is its composition? Why is butter containing butter-milk liable 
to deteriorate? How does the melting of butter tend to preserve it ? What is the chem- 
ical condition of milk ? What causes it to coagulate ? What is cheese ? How is it manu- 
factured? 



490 



ORGANIC CHEMISTRY, 



rated from the whey by straining ; then drained, mixed with a portion of salt, 
and sometimes other condiments, and subjected to pressure. The product is 
cheese, which, when kept for several months in a cool situation, undergoes a 
kind of putrefaction, and obtains thereby a peculiar taste and odor. The 
goodness of cheese depends upon the proportion of cream left in the milk, 
and upon the method of its manufacture. 

823. B 1 o o d. — " The blood is the general circulating fluid of the animal 
body, the source of all nutriment and growth, and the general material from 
which all the secretions, however much they may differ in properties, are 
derived. It also serves the scarcely less important office of removing and 
carrying off from the body principles which are hurtful, or no longer re- 
quired." 

In all vertebrated animals, viz., man, mammals, birds, reptiles, and fishes, 
the blood has a bright red color ; while in the invertebrata, as insects, the 
Crustacea, mollusca, and zoophytes, it is very often colorless, but sometimes 
tinged with red, yellow, green, or other hues. 

824. Composition of the Blood . — The blood, as seen under the 
microscope, circulating in the vessels, appears to consist of a colorless liquid, 
holding in suspension little globules, called corpuscles, or cells. Some of 
these, in man, are white, but most are red, and give to the blood its color. 
The red corpuscules vary in size and shape in different animals, and the mi- 
croscopist, taking advantage of this circumstance, is enabled, even after the 
lapse of years, to distinguish in the dried stain, human from animal blood, 
and also to pronounce with certainty whether a particular spot is occasioned 



Fig. 240. 




Fig. 241. 



by blood or some other liquid. 

In man they appear as circular 

flattened disc, having an average 

diameter of l-3200th of an inch, 

and a thickness of l-124,000th. 

In reptiles they are elliptical and 

larger than in man. Fig. 240 

represents their appearance in 

human blood magnified 500 

diameters, and Fig. 241 their ap- 
pearance in the blood of a frog, 

magnified 250 diameters. When 
dried, they form, in man, on an average, about 13 per cent, of the whole 
weight of fresh blood. 

In man and all warm-blooded animals, the color of the blood in the arteries 
is of a bright scarlet, while in the veins it is dark red. These changes of 
color are primarily due to the action of atmospheric oxygen upon the blood, 
while passing through the lungs. 




Questions. — What is the blood ? "What is said of its color? What is its appearance 
under the microscope ? What is said of the blood corpuscles? What is said of the color 
of the blood in the veins and arteries ? 



ANIMAL ORGANIZATION AND PRODUCTS. 491 

The fluid of the corpuscles contains the coloring matter of the blood, which 
is called h&matiMe, particles of fat, a colorless substance called globuline, which 
resembles caserne in its properties and composition, and various saline mat- 
ters. Htxmatine is remarkable for containing, as an essential ingredient, oxyj}. 
gjijrqn, which may be easily extracted and tested by igniting a little dried 
clot of blood in a crucible, and digesting the residue with liydrQchloric acid ; 
the solution thus obtained, gives Prussian blue, with ferrocyanide of potassium. 

The colorless corpuscles of the blood are supposed to contain principally 
fat. 

The colorless liquid surrounding the blood corpuscles is water, holding in 
suspension or solution a great number of different substances, viz., albumen, 
fibrine, fat, and a great number of salts, such as the phosphates of soda, 
lime, and magnesia, the carbonates and sulphates of potash and soda, and 
the chlorides of potassium and sodium. It also contains several gases, oxy- 
gen, carbonic acid, and nitrogen, arising from the action of air in the lungs. 
A healthy, full-grown, average sized man, contains about 20 lbs. of blood ; 
1,000 parts of which consist of 700 to 790 parts water, GO to Y0 albumen, 2 
or 3 fibrine, 1-4 to 3 of fat, and 10 of mineral salts. 

The heat of the blood depends in a great degree upon the activity of the 
process of respiration. In man, when in a state of health, its temperature re- 
mains, under almost all circumstances, in the extreme cold of the polar re- 
gions and under the tropics, at about 98° P. In birds, the temperature is 
sometimes as high as 108° P. In fishes, it is about that of the water in 
which they live. Animals whose temperature is but little higher than tho 
medium in which they live are called cold-blooded, while those whose tem- 
perature is warmer than the air which surrounds them, are called warm- 
blooded. 

In i^s ordinary state, the blood has a decidedly alkaline reaction, a saline 
taste, and a peculiar odor. "When taken from the living animal, it soon un- 
dergoes spontaneous coagulation, and separates into two portions ; one, a 
pale, yellowish, slimy fluid, called the serum, the other a gelatinous, red 
mass, called the clot, or coagulum. The former contains nearly all the albu- 
men and saline constituents of tho blood, while the latter, as before stated, 
is produced by the coagulation of the fibrine, which, " although constituting, 
when dry, a very small proportion of the whole, yet in the bulky and swol- 
len condition in which it separates, is voluminous enough to entangle in its 
net- work of fibers the whole of the coloring matter, and cause its mechanical 
separation." The cause of the coagulation is not fully determined; the ad- 
dition of certain £aiine,substances, such as a saturated solution of cWorij^ 
of sodium, either retards or prevents it ; while alurn, and the oxyds of zinc and 

Qtjesttons. — What is the composition of the Mood corpuscles ? What of the fluid sur- 
rounding the corpuscles ? What quantity of blood is contained in a healthy man ? What 
are the general constituents of the blood? What is said of the heat of the blood? What 
are -warm and cold-blooded animals ? What change does the blood undergo when drawn 
from the veins ? What is the serum ? What the clot ? 



492 ORGANIC CHEMISTRY. 

copper, promote it. The blood of persons also who have died a sudden, vio- 
lent death by some kinds of poison, or from mental emotion, is usually found 
in a fluid state.* - — f 

825. Nutrition . — The constant waste of the animal body consequent 
on the discharge of the various functions necessary to the support of life, re- 
quires that an equally constant supply of new material should be afforded, 
from which the repairs and renewals of the system may be effected. This 
end is accomplished through the agency of food, which in all animals con- 
sists of protein in its various forms (albumen, fibrine, caseine, etc.), starch, 
sugar, gum, and fat, to which, in the case of flesh-eating animals, gelatine 
must be added. Food, or nourishment from without, can, however, be only 
made available for the wants of the system by being first converted into 
blood, and this is effected through the agency of various processes, which are 
collectively termed digestion. 

826. Digestion . — The various acts of the function of digestion are as 
follows : — From the mouth, where the food is chewed by the teeth and moist- 
ened by the saliva, it passes into the stomach. 

The saliva is secreted by glands which open into the interior of the mouth, 
and consists chiefly of water, holding in solution about 1 per cent, of saline 
matter. The quantity of saliva produced in a full-grown, healthy man, in the 
course of 24 hours, varies from 8 to 21 ounces. Its chief office seems to be 
to dilute the food and assist mastication and deglutition ; but it is also sup- 
posed to act chemically, through the agency of a peculiar organic substance 
contained in it, termed ptyaline, which, like diastase, is capable of converting 
the starch and gum of the food into sugar. Its' action, however, in this re- 
spect, is probably very limited. 

The food, having reached the stomach, is subjected to the action of a pe- 



* "No other component part of the organism," says Liebig, "can be compared to 
the blood, in respect to the feeble resistance -which it offers to external influences. It is 
not an organ which is formed, but an organ in the act of formation ; indeed it is the sum 
of all the organs which are being formed. The chemical force and the vital principle 
hold each other in such perfect equilibrium, that every disturbance, however trifling, or 
from whatever cause it may proceed, effects a change in the blood. In fact, it possesses 
so little permanence, that it can not be removed from the body without immediately suf- 
fering a change, and can not come in contact with any organ in the body without yielding 
to its attraction. The slightest action of a chemical agent upon the blood exercises an 
injurious influence ; even the momentary contact of the air in the lungs, although ef- 
fected through the medium of cells and membranes, alters the color and other qualities 
of the blood. Every chemical action propagates itself through the mass of the blood : 
for example, the active chemical condition of the constituents of a body undergoing de- 
composition, fermentation, putrefaction, or decay, disturbs the equilibrium of the chem- 
ical force, and the vital principle in the circulating fluid. Numerous modifications in the 
composition and condition of the compounds produced from the elements of the blood re- 
sult from the conflict of the vital force with the chemical affinity, in their incessant en- 
deavor to overcome each other." 

Questions. — What is the office of food ? Of what does the food of animals consist ? 
What change is necessary to render food efficacious ? What is the first process of di- 
gestion ? What is the saliva ? What is its constitution ? What its action ? 



ANIMAL ORGANIZATION AND PRODUCTS. 493 

culiar fluid, called the gastric juice, which flows out of minute openings in 
the inner surface — or mucous membrane, as it is called— of the stomach. 
This fluid possesses the power of dissolving, at the temperature of the body, 
the nitrOgenized alimentary principles, such as albumen, fibrine, etc., but ex- 
erts no solvent action upon starchy or fatty substances. These last, however, 
through the joint action of the saliva and the uniform warmth and motion of 
the muscular walls of the stomach, are all brought into a semi-fluid state. In 
what manner the gastric juice is enabled to effect the reduction of nitrOgen- 
ized food to a nearly fluid condition, is not known. It is said to contain 
free hydrochloric acid, and an organic principle called pepsin, and to the 
joint influence of these two the solvent power of the gastric juice has been 
attributed.* 

The amount of gastric juice secreted by the stomach of a well-fed, grown 
man, has been estimated at from 60 to 80 ounces in every 24 hours. 

Digestion generally commences immediately after the introduction of food 
into the stomach, and is usually finished in about four hours — the food being 
converted into a grayish, gruel-like, slightly acid pulp, called chyme. This 
chyme passes from the stomach into the upper part of the small intestines, 
called the duodenum, where it is moistened by two saliva-like liquids, the bile 
and the pancreatic juice, which are secreted by peculiar organs termed res- 
pectively the gall-Madder and the pancreas. The action of the bile on the 
food is not well known, but the pancreatic juice acts instantaneously on tho 
non-nitrogenous alimentary substances, converting starch, etc., into sugar, 
and the fatty matters into an emulsion which renders them fit for absorption. 
After undergoing the action of these liquids, the nutritious matter presents a 
uniform milky appearance, and is termed chyle. In this condition it is nearly 
all absorbed by a system of vessels called the lacteals, which terminate in a 
common reservoir — the thoracic duct — which in man is about the size of a 
large goose-quill. The thoracic duct terminates in a large vein near the left 
shoulder, anl into this the chyle is discharged and passes forward to the 
lungs, where it assumes a red color and becomes blood, f 

* Some years since a French Canadian by the name of St. Martin, -was severely injured 
in the side by the explosion of a gun, but the wound finally healed, leaving a permanent 
orifice in the walls of the stomach through which food could be introduced, and all the phe- 
nomena of the digestion observed. From the stomach of this person, also, gastric juice 
has been taken out by means of a little cup, and chemically examined. Professor F. S. 
Smith, of the Pennsy'vania Medical College, who examined the gastric juice thus obtained 
in 1S57, states that it contains hardly any hydrochloric acid, but much lactic acid ; and to 
this latter agent he ascribes the constant acid reaction of the stomach. It has also been 
shown by observations made through this subject, that the food introduced into the stom- 
ach is caused to revolve continually around its interior, the revolutions requiring a period 
of from one to three minutes. 

t It is not to be understood that all food lingers in the stomach for the space of several 

Questions. — What change does the food undergo in the stomach? What is the gastric 
juice ? What quantity of gastric juice is secreted by the stomach ? What period is usu- 
ally required for digestion? What is chyme ? What takes place when the food leaves 
tho stomach? What is the function of the bile and pancreatic juices? What is chyle? 
What becomes of the chyle ? 



494 ORGANIC CHEMISTRY. 

That part of the food (chyle) which is insoluble, or unfit for assimilation, is 
left unabsorbed by the lacteals, and passes off through the intestines in the 
form of excrementitious matter. "How effectual the digestive process is in 
exhausting what we eat of its nutritive matter may be judged of from the 
fact, that a healthy, grown man, fed with ordinary diet, rejects of undigested 
and of wasted or used up matter, both taken together, only from four to six 
ounces. And this rejected matter consists of— 

Water 3 to 4£ oz. 

Organic matter Of to 1 1 " 

Mineral matter, chiefly phosphates 0£ to Of " 

Total 4 to 6 oz. 

Or he discharges one to one and a half ounces of dry solid matter daily. "~^- 
Johnson.* 

***. Respiration . — All animals as well as vegetables require, for the 
proper performance of their various functions and their continued existence 
in a living state, a free supply of atmospheric air as well as a supply of food. 
It is also necessary that this air should have free access to the interior of their 
structure, and the act or process by which this is accomplished is termed 
Respiration. 

The organs by which the act of respiration is performed differ essentially 
in different species of animals. In the lowest types of the animal kingdom, 
as the polypes, respiration is accomplished exclusively through the skin. In- 
sects also draw in air into their system, or in other words, breath, by means 
of organs called tracheae, or wind-pipes — tubes which penetrate in various 
directions through their bodies, and terminate externally in little orifices 
called stomata. If we smear the body of an insect, as a wasp, with thick oil, 
we close up the stomata, and the insect speedily dies of suffocation. All 
vertebrate animals are endowed with localized organs of respiration, which 
are termed lungs, or gills. In man and the higher animals, the " lungs con- 
sist of two rounded, oblong, somewhat flattened masses, of very cellular sub- 
stance, situated in the cavity of the chest, and communicating with the at- 

hours. Soups and nutritious fluids which require no "breaking down" in the stomach, 
pass from the stomach into the intestines in a very short period. Neither is nutriment 
taken up wholly through the lacteals of the intestines, but a certain portion, in a fluid 
state, by the action of endosmotic force, passes through the walls of the stomach, and is 
mingled with the general blood. 

* The cause of the peculiar odor of fcecal matter is in great measure unknown, although 
scientific ardor has induced some chemists to undertake most repulsive investigations with 
a view of obtaining information on the subject. By treating fresh night soil with alcohol 
two principles have been extracted, viz., a crystalline, slightly alkaline substance, named 
ezcretine, and an acid called excretolicacid ; but little, however, is known concerning them. 
It has also been ascertained that when albuminous compounds are heated with hydrate 
of potash, and the residue distilled with sulphuric acid, an odor characteristic in an in- 
tense degree of fcecal matter is produced. 

Questions. — What, becomes of the unassimilated matter ? What is respiration ? How 
is respiration effected in different animals ? What is the constitution of the lungs in man 
and the higher animals ? 



ANIMAL ORGANIZATION AND PRODUCTS. 495 



Fig. 242. 




mosphere through the wind- 
pipe, or tracheae. The general 
form of the human lungs is 
represented in Fig. 242. The 
air or wind-pipe, a b, as it de- 
scends from the throat, branch- 
es off into large (bronchial) 
tubes, c c, and these again into 
smaller and still smaller, and 
finally into hair-like, or capil- 
lary vessels. These capillary 
tubes, in turn, communicate 
with little air-cells contained 
in an elastic membrane, so 
minute that the number exist- 
ing in the lungs of a full-grown 
man is estimated at 600 mil- 
lions, and between, or imbed- 
ded in these cells, blood-vessels 
equally minute are distributed 
in every direction. The ap- 
pearance of the air-cells and blood-vessels of the lungs, as seen under the 
microscope, is represented in Fig. 243. 

The motion of the lungs in respiration is analogous 
to the motion of the leather of a pair of bellows. 
"When we inhale, the cavity of the chest or thorax is 
expanded by muscular action, and a vacuum is formed 
around the lungs, in consequence of which the exter- 
nal air instantly rushes in and penetrates to the re- 
motest parts of the cellular substance. When we ex- 
hale, the thorax contracts, and the air contained in the 
lungs is expelled, the muscles of the wind-pipe at the 
same time contracting in order to assist the process. 
In ordinary respiration, a man makes 17 or 18 respi- 
rations per minute, during each of which he draws 
in about 20 cubic inches of air, or between 3 and 4 
thousand gallons per day. In man also the skin is to 
some extent a respiratory organ, through which air 
enters and escapes, as it does from the air-vessels of 
the lungs, though less rapidly.* 



Fig. 243. 




* When a portion of the skin has been burned, it is no longer capable of exercising the 
function of respiration, and the lungs are therefore obliged to perform extra duty, and 
Buffer in consequence. Hence diseases of the lungs are a frequent result of extensive 
burns. 

Questions. — What is the mechanical action of breathing? What amount of air enters 
the lungs by respiration ? Is the skin a respiratory organ ? 



496 ORGANIC CHEMISTRY. 

The composition of the air which escapes from the lungs is not the same 
as that which enters, and is found to contain a greatly increased quantity of 
carbonic acid and vapor of water, and a diminished percentage of oxygen ; 
the quantity of nitrogen, however, remains nearly unaltered. 

The amount of pure carbon which is thrown off from the lungs of a full-grown 
man, in the form of carbonic acid, in a space of 24 hours, varies from 5 to 
15 ounces ; while the quantity which escapes from the skin also during the 
same period, by respiration, is estimated at from 50 to 60 grains. The 
amount of water exhaled from the lungs and skin in 24 hours probably 
averages about 3 or 4 pounds. 

The lungs extract or absorb from the air which enters them from one 
seventh to one fifth of its oxygen, and the absolute weight of the oxygen 
thus introduced into the system in a day, is estimated to be equal to about 
one fourth of the weight of the whole food, solid and liquid, which an ani- 
mal consumes. The absorption of oxygen takes place in the minute air- 
cells of the lungs, through the thin membraneous walls of which it passes by 
the action of endosmosis into the adjacent blood-vessels, and combines with 
the blood contained in them, imparting to it the bright scarlet color which is 
characteristic of arterial blood. 

827. Uses of Respiration . — From what has been already said, it 
must appear evident that the principal object of respiration is to introduce 
oxygen into the blood, which contains the nutritive portion of the food taken 
into the stomach. The purpose which oxygen subserves in the blood is 
three-fold : — 

I. It assists in building up the substance of the body. The composition of 
gluten, albumen, and the other nitrogenized vegetable principles, is, as has 
been before stated, very nearly the same as that of the corresponding prin- 
ciples in animal tissues ; yet chemical investigations have shown that the 
former require to be combined with a certain proportion of oxygen before 
they can become incorporated in the substance of the body. This oxygen 
is supplied through the lungs, but the quantity thus used for restorative pur- 
poses is small. 

II. It assists in removing waste and effete matters from the system. The 
expenditure of every kind of force in the animal system is accompanied by, 
or requires an expenditure or change in animal matter. The particles of 
matter which have once undergone such change, or have once discharged 
their functions, become inoperative, or waste, and their removal from the sys- 
tem is necessary to a continuance of healthy action. Now the agent which 
mainly effects the change in the first instance, and removal of the waste pro- 

Questions. — What is the composition of the air which escapes from the lungs? What 
amount of carbon passes from the system by respiration ? What amount of water is ex- 
haled from the lungs and skin ? What proportion of oxygen is absorbed by the lungs 
from the air ? In what part of the lungs does the absorption of oxygen take place ? What 
Is the use of respiration ? What purpose, subserved by oxygen in the blood, is first men- 
tioned? What is the second end attained to? How does oxygen remove waste matters 
from the system ? 



ANIMAL ORGANIZATION AND PRODUCTS. 497 

ducts in the second, is the oxygen absorbed by the blood in the lungs. 
Thus muscle, by the addition of oxygen, becomes decomposed, aud passes in 
a state of solution into the veins, from whence it is secreted by various organs, 
and finally thrown out from the system. 

Urine . — The channel through which most of the products of the de- 
composition of the azotized todies and many of the waste mineral salts pass 
out of the body, is the urine. This liquid, which is secreted by the kid- 
neys from the blood, also serves to remove any superfluous water from the 
system. Its principal constituents are two complex organic substances 
termed urea and uric acid, which are composed of carbon, hydrogen, nitro- 
gen, and oxygen, and readily furnish by their decomposition various salts of 
ammonia. In addition to these products, urine contains phosphates of lime, 
magnesia, and soda, sulphates of potash and soda, chloride of sodium, lactic 
acid, and certain imperfectly known organic principles, including a coloring 
and an odoriferous substance. All these substances exist in the urine dis- 
solved in water, which constitutes more than nine tenths by weight of the 
whole secretion. 

III. The absorption of oxygen produces animal heat This is accomplished 
by the oxydation or combustion of the constituents of the non-nitrogenized 
food existing in the blood. The reasons which lead us to this inference may 
be briefly stated as follows : — 

If a fat animal be deprived of nourishment for some days, it will rapidly 
diminish in weight. This result is the necessary consequence of the fact, 
that the animal is continually throwing off carbonic acid and water from the 
lungs and skin, and urea and mineral constituents through the excretory 
organs, and receiving no food to replace them. 

If we examine the condition of an animal after this period of starvation, we 
find the loss of weight and substance is most remarkable in the fat of the 
body, which has diminished in far greater proportion than any of its other 
constituent substances. Careful examination also shows that this fat has 
not passed off as liquid or solid excrement, but has been converted in the 
blood, by oxydation, into carbonic acid and water, and in this condition has 
been breathed away through the lungs and skin. If, however, instead of 
starving the animal, we give it abundance of fat in its food, then the fat of 
its own body will suffer no diminution, but the oxygen taken into the blood 
will transform the fat of the food into carbonic acid and water, and these will 
be breathed out of the lungs as before. The same end will also be attained 
if instead of fat we give food, like starch and sugar, which is analogous to 
fat in its composition. — Johnson. 

Now when carbon and hydrogen compounds, i. e., fat, starch, sugar, etc., 
are oxydized or burned in the open air, carbonic acid and vapor of water are 
produced, and heat is evolved. The same action must necessarily be attended 
with the same results in the body, and we have, therefore, an explanation of 

Questions. — What is urine? What is the composition of this secretion? What third 
purpose is suhserved hy oxygen ? How does the absorption of oxygen occasion animal 
heat ? What reasons lead to this inference ? 



498 ORGANIC CHEMISTRY. 

the phenomenon of animal heat .Furthermore, all experiments show that the 
amount of heat generated by burning (oxydating) a certain quantity of fat, 
etc., is the same, -whether the combustion takes place in a furnace or in the 
animal system. 

The oxydation of fat and the other constituents of the blood is supposed to 
take place mainly in the minute vessels or passages, termed capillary vessels, 
which unite the ultimate subdivisions of the veins and arteries, and are dis- 
tributed over every part of the body where nervous influence is perceptible. 
]n these, the arterial blood, coming from the lungs and possessing a scarlet 
color, gives up its oxygen to the substances with which it is brought in con- 
tact, and receives in return the products of oxydation, carbonic acid and 
water. It also changes in color from a bright to a dark red, and returning 
through the veins to the lungs, through the action of the heart, passes 
into the minute blood-vessels of the lungs, which are surrounded by the air- 
cells. Here the carbonic acid and excess of water pass out through the 
walls of the membraneous tissue inclosing them through endosmotic action, 
and by the act of exhalation are forced into the air ; while at the same time 
oxygen from without is by similar means carried inward, and the blood, re- 
stored to its arterial condition, returns upon its circuit to effect the same 
changes and undergo the same transformation. 

Animals whose respiratory organs are small and imperfect, and vdiich, there- 
fore, consume but a comparatively small amount of oxygen, possess a bodily 
temperature but little elevated above that of the medium in which they live ; 
animals, on the contrary, whose lungs are large in proportion to their bodies, 
and respire frequently, possess the highest bodily temperature. In man, 
the mean temperature of the body is about 98° F. The temperature of a 
healthy child, who consumes proportionally more oxygen and respires more 
frequently than an adult person, is somewhat higher, 102° F. In birds the 
temperature is from 104° to 10S° F. The temperature of the same animal 
also at different times, varies with the activity of the respiration. TVhen the 
blood circulates slowly, and the temperature is low, the quantity of oxygen 
consumed is comparatively small ; when, on the contrary, the circulation by 
vigorous exercise or labor is accelerated, a large quantity of oxygen disap- 
pears, and the animal heat rises. 

828. Nature and Functions of Food . — A careful consider- 
ation of all the facts connected with the subjects of nutrition and respiration, 
has led to the division of all animal nutriments into two great classes, viz., 
those which are devoted to the repair and nutriment of the body, and those 
whose duty it is to furnish animal heat by combustion in the blood. The 
former have been termed by Liebig the plastic elements of nutrition, and the 
latter the elements of respiration. 

Questions. — Explain the manner in which the oxydation of matter takes place through 
the circulation. What relation exists bet-ween the frequency of respiration and the ani- 
mal temperature ? How does vigorous exercise increase the temperature of the system ? 
Into what two classes are all animal nutriments divided ? What are called plastic ele- 
ments of nutrition ? 



ANIMAL ORGANIZATION AND PRODUCTS. 499 

The substances included in the first class are exclusively the protein com- 
pounds, viz., vegetable fibrine (gluten), vegetable albumen, vegetable caseine, ani- 
mal flesh and blood. These only have the power of reproducing muscular 
and nervous material, and these only cau afford nourishment and support in 
the strict sense of the term. In a state of great purity, these bodies, however, 
are not alone sufficient for the due maintenance of the vital powers. The ex- 
periment has been frequently tried on animals, and always with a negative 
result. Certain of the non-azotized substances, and certain saline compounds 
which are always present in natural food, are also required. 

The elements of respiration are fat, starch, gum, sugar, alcohol, etc. Gelatine 
also probably belongs to this class, inasmuch as it has never been found in 
the blood, and is supposed to be converted in the process of digestion into 
sugar and ammonia compounds. These substances alone, are still less capa- 
ble of supporting life than the simple protein principles. 

829. The quantity of food required by an animal for purposes of nutrition 
or respiration varies greatly under different circumstances. When the waste 
of muscular or nervous material is great, a largo supply of nitrogenized food, 
or that rich in the elements of nutrition will be required. "When the body is 
exposed to severe cold or to violent exercise, the loss must be met by a pro- 
portionate increase in food rich in the elements of respiration. In the food 
most abundantly provided by nature for animals, the cereal grains, vegetables, 
and ordinary meat, both forms of nutriment abound. In tropical countries, 
where the loss of animal heat is small, and where muscular power and mo- 
tion are less required and employed, the waste of the body is greatly dimin- 
ished, and a comparatively small quantity of food, both for fuel and nourish- 
ment, is required. The inhabitants of such countries, therefore, live mainly 
on rice and fruits— substances which contain a large amount of oxygen, and 
are therefore less adapted to furnish animal heat by oxydation in the blood. 
The desire for animal food, under such circumstances, is very slight, and is 
sometimes altogether absent. In cold countries, on the contrary, a greater 
quantity of the elements of respiration is needed to generate the proper 
amount of heat, and at the same time, as the air is much colder and therefore 
more condensed, a larger quantity of oxygen is taken into the lungs at each 
inspiration. The inhabitants of such countries, therefore, consume enormous 
quantities of food of a fatty nature — substances rich in hydrogen and emi- 
nently combustible, and which, weight for weight, generate a larger amount 
of heat, when oxydated or burned in the blood, than any other products that 
can be taken as food. Navigators exposed to the intense cold of the Arctic 
regions, share to a certain extent with the Esquimaux, the same liking for 
blubber and train oil, which in milder latitudes they regard with aversion. 

830. The fat and oils found in animal tissues appear to be stores of respi- 

QtTESTiosrs. — Can these substances in a state of purity alone suffice for food ? What 
are the elements of respiration ? What is said of the quantity of food required by ani- 
mals for the purposes of nutrition or respiration ? What effect has climate on the wants 
of the system ? What is said of the accumulation of fat and oils in the animal system? 



500 ORGANIC CHEMISTRY. 

ratory food, laid up by nature against time of need. They accumulate most 
in the system when fat itself, or the compounds containing its elements, are 
supplied in excess as food, and when the animal, through lack of active exer- 
tion, absorbs but little oxygen, and consequently experiences but little waste.* 

When the supply of food is wholly withheld from the animal, the fat, as 
the most combustible substance, and the one most capable of supplying car- 
bon and hydrogen to meet the wants of respiration, rapidly disappears. When 
this has all been consumed, the muscles are next attacked, and last of all the 
substance of the brain and nerves ; then insanity intervenes, and the animal 
dies, like a lamp or candle that has been burnt out. 

831. The main difference between beef and bread, which two substances 
may be regarded as the representatives, or types of animal and vegetable 
food, is, first, that the flesh does not contain starch, which is so large an in- 
gredient in vegetable products ; and second, that the proportion of fibrine in 
ordinary flesh is about three times greater than its corresponding element, 
gluten (vegetable fibrine), is in bread. It therefore follows, that a pound of 
beef-steak is as nutritive as three pounds of wheaten bread, in so far as the 
nutritive value of food depends upon this one ingredient. In meat, also, fat 
to a certain extent represents and replaces the starch of vegetable food. 

The relative nutritive value of the different meats is as follows : beef is the 
most nutritious, then chicken, pork, mutton, and veal. Of vegetable produc- 
tions, the cereals generally rank first as respects nutritive value ; after them 
come the seeds of leguminous plants, peas, beans, etc. ; then the cabbage, onion, 
turnips, carrots, potatoes, rice, and watery fruits. " The dried potato is less 
nutritive, weight for weight, in the sense of supporting the strength and en- 
abling a man to undergo fatigue, than any other extensively used food of 
which the composition is known, with the exception of the rice and of the 
plantain." Fish in general contains more fibrine and less fat than flesh-meat, 
and is highly nutritious. 

Salted meat is less nutritious than fresh meat. The application of salt to 
meat causes the fibers to contract, and the juices to flow out from its pores. 
Hence fresh flesh over which salt has been strewed is found, after the lapse 
of a little time, to be swimming in its own brine, although not a drop of 
w r ater has been added. The juice thus extracted contains a large proportion 
of the nutritive constituents of the meat, i. e., albuminous compounds, with 
the alkaline and earthy phosphates. Hence the continued and exclusive use 
of salt provisions occasion a disease called the scurvy, in which the blood 
becomes impaired mainly through a lack of the soluble mineral salts which are 
removed from the meat by the brine. i 



* This principle is applied in the fattening of animals, by compelling them to remain 
inactive by confinement in stalls or pens, and at the same time supplying them plenti- 
fully with rich, oily food. 

Questions. — What takes place when the animal is deprived of food ? What is the dif- 
ference between beef and bread as respects nutritive qualities? What is the relative 
values of different meats and vegetables? What is said of salted meat? 



ANIMAL ORGANIZATION AND PRODUCTS. 501 

The preservation of fresh meat by salting is due to a separation of its 
water, to an exclusion of air through a contraction of the fibers of the meat, 
and upon the formation of a compound of the flesh and the salt, "which does 
not readily undergo decay. 

832. Relation between Animals and Plants . — All the 
various forms of matter which are essential to the existence of living organ- 
isms are in a constant state of circulation. Thus, the essential constituents 
in the formation of vegetable products are carbonic acid, ammonia, and water. 
Plants absorb these from the soil or from the atmosphere, and, under the in- 
fluence of sun-light and the vital principle, rearrange and organize them into 
vegetable tissue, starch, sugar, fat, and the protein compounds. These sub- 
stances constitute the food of animals, and after employment in their systems, 
and after passing through various decompositions, they are again restored to 
the earth and the atmosphere in the form of carbonic acid, water, and ammo- 
nia : and are once more rendered capable of assimilation by plants. Thus an 
uninterrupted and perpetual chain of vital phenomena is established from in- 
animate matter to the living plant, and from the living plant to the living, 
sentient animal, and the products of one order of beings become the suste- 
nance of the other. 

833. Conclusion . — " What has been called organic chemistry is no- 
thing but a name, and a wrong one. There is really no such science ; it is 
only the chemistry of inorganic forms, of substances that have been living 
but are now dead — of the mere refuse and remains of organization. The 
composition of those favored materials from which the vegetable world weaves 
its tissues — water, carbonic acid, and ammonia — is known. The composition 
of the proximate principles which are extractabl9 by easy processes from dead 
plants and animals, is also known. But the composition of the truly living 
tissues neither is, nor can be understood. They die the moment chemistry 
puts her finger on them. She can trace the constructive elements into the 
structure of the living animal or plant, and out of it, but not in it. What 
may be their mode of arrangement, or of their possible ingredients in matter 
which is genuinely alive, scientific investigation fails to reveal. The living 
frame of the meanest animal or plant is sacred and enchanted ground, where 
the chemist can only take the shoes off his feet and confess the sanctity and 
inviolability of life." 

Questions — How does salt preserve meat ? "What is said of the relation of animals 
and plants ? What does organic chemistry really consider ? Do we actually know the 
composition of a living tissue ? 



APPENDIX. 



Apparatus — The apparatus essential for illustrating and facilitating 
the study of chemistry, need not be of necessity expensive or complex. With 
the somewhat popular idea, however, that a course of experimental chem- 
istry can be successfully conducted with an apparatus improvised from a few 
bottles, tobacco-pipes, and glass tubing, the author has no sjmipathy. Chem- 
ical experiments are most easily and successfully performed with apparatus 
especially constructed for the purpose, and what is saved in expense by 
using imperfect and unsuitable materials, will be more than lost in time and 
vexation of spirit. It is no doubt true that many eminent chemists have in- 
stituted important investigations, and performed brilliant experiments, with 
exceedingly simple or imperfect apparatus ; but it is also equally true, that 
the tact and ability required to overcome the inherent difficulties of such an 
undertaking, have been deemed sufficiently singular to occasion especial 
comment. In short, it is only the operator rendered skillful by long expe- 
rience and practice who is able to work successfully in chemistry with poor 
materials, and not the tyro. 

We believe, therefore, the most practical advice that can be given to teachers 
and students who are lacking in experience, is to procure the very best appa- 
ratus their resources will admit of, as being in the end the cheapest and most 
serviceable. 

In purchasing apparatus it will be found advisable, also, to first send to 
some one or more of the prominent dealers in Boston, New York, or Phila- 
delphia, for an illustrated and priced catalogue of their stock. In this way 
the purchaser will be enabled to make his selections most judiciously and 
economically. 

The following articles will be found most serviceable and indispensable for 
a short course of chemical experimentation: — A copper flask, with adjustable 
tube and collar, for generating oxygen gas ; a retort stand with movable 
rings of various sizes ; a glass (4 oz.) spirit-lamp ; 2 dozen test tubes and 
stands; 2 wide-mouth, stoppered glass jars, or receivers; 2 tall and plain 
cylindrical air-jars (see Fig. 87) ; 4 to 6 flat-bottom, thin glass flasks, suitable 
for generating hydrogen, hydrosulphuric and carbonic acid gases (see Figs. 
101, 126, 130); 1 one quarter pint stoppered retort and receiver; 1 one half 
pint do., plain ; a gas-bag, provided with stop-cock and bubble-pipe ; a set 
of small porcelain basins ; glass tubing and small glass rods for stirrers, etc. ,• 



APPENDIX. 503 

2 small glass funnels ; a deflagrating ladle or spoon ; a small wedge-wood 
mortar and pestle; a blow-pipe; platinum foil and wire; filtering-paper; 
test papers ; set of cork-borers ; a steel spatula ; a strip of sheet caoutchouc ; 
a round and a three-cornered file for filing corks, cutting glass tube, etc. ; a 
nest of earthen crucibles ; and two small porcelain crucibles. 

A pair of gasometers, oxygen and hydrogen, arranged in such a way as to 
admit of being used conjointly as a compound blow-pipe (see Fig. 102) are al- 
most indispensable. They are now made of small size, and at a very moder- 
ate expense, and constitute an exceedingly durable, serviceable, and orna- 
mental article of laboratory furniture. A Berzelius spirit-lamp (see Fig. 173) 
will obviate, to a great degree, the necessity of ever using a furnace. The 
operator can easily arrange a pneumatic trough after any of the models given 
on page 197, to suit his own convenience. 

In addition to the articles thus specified, there are many others, such as a 
small galvanic battery, an apparatus for decomposing water, specific gravity 
bottles, thermometers, scales and weights, etc., etc., the necessity for which 
will depend in a great measure upon the extent and fullness of the course 
of experimentation prescribed or adopted. 

In regard to chemical reagents, the following is a list of the more impor- 
tant : the acids, sulphuric, hydrochloric, nitric, acetic and oxalic ; potassium, 
sodium, ammonia (aqua), carbonate of ammonia, sal-ammoniac, phosphorus, 
caustic potash, carbonate of soda, black oxyd of manganese, chlorate of pot- 
ash, alum, sulphur, bone-black, iodine, bleaching powder, acetate (sugar) of 
lead, iodide of potassium, sulphate of copper (blue vitriol), sulphate of iron 
(green vitriol), borax, bi-chromate of potash, ferrocyanide of potassium (yel- 
low prussiate of potash), fluor spar, arsenious acid, metaUic antimony, fine 
iron-wire, sheet zinc, tin foil, copper turnings, chloride of barium, chloride of 
strontium, lime water, metallic mercury, chloride of mercury (corrosive subli- 
mate), saltpeter, nitrate of silver, alcohol, ether, and bees- wax. 

Of the above-mentioned reagents, it is recommended to have the following 
(in solution) arranged upon a convenient stand, or tray, in clear glass bottles, 
fitted with ground glass stoppers, and of the capacity of about a half pint : 
sulphuric acid dilute ; do. strong (oil of vitriol) ; nitric dilute ; do. concen- 
trated ; hydrochloric acid ; acetic acid ; oxalic acid ; aqua ammonia ; carbonate 
of ammonia ; chloride of ammonium (sal ammoniac) ; chloride of barium ; 
lime water ; caustic potash ; caustic soda ; carbonate of soda ; sulphate oi 
copper ; ferrocyanide of potassium ; chlorine water ; chloride of mercury (cor- 
rosive sublimate) ; bi-chromate of potash ; sulphindigotic acid ; acetate of 
lead ; perchloride of iron ; alcohol and ether. Also the following in solution 
in 1 or 2 ounce bottles : iodide of potassium ; nitrate of silver ; chloride of 
platinum. Reagent bottles suitable for this purpose, with printed labels and 
formula, may be obtained of all dealers in chemical apparatus. 

Most of the reagents needed for ordinary chemical experiments are ex- 
ceedingly cheap, and may be procured of any druggist. 

The teacher would, however, do well to bear in mind, that if his resources 
ki apparatus and chemical reagents are limited, he can supply himself, almost 



504 APPENDIX. 

without cost and with but little trouble, with abundant materials for render- 
ing his instructions both interesting and practical. Thus, he has in the com- 
mon varieties of coal, gas-carbon, plumbago (black-lead), coal-tar and coal- 
oils, all readily accessible — the best materials for illustrating the study of 
carbon ; and in wood-ashes, common potash, carbonate of soda, Jime, mar- 
ble, spar, oyster-shells, gypsum, chalk, Epsom salts, common salt, and alum, 
the best illustrations of the alkalies, the alkaline earths, and their compounds. 
In like manner, specimens of most of the ores, the common metals, and their 
oxyds, the products of the smelting furnace, the glass-house, and the pottery, 
with a great variety of organic compounds, may be easily collected ; and it 
is by such simple and common objects that the applications of chemistry to 
the wants and employment of every-day life are made most familiar. 

The operator will also find it an advantage, in preparing and arranging 
apparatus, to have some work on chemical manipulations for consultation ; 
such as Morffit's, Noad's, or Williams' Chemical Manipulations, or Bowman's 
Practical Chemistry. 



The present work constitutes the third of a Series of Educational Text- 
books on Scientific Subjects, arranged upon the same general plan by the 
same author — the two others being "Wells' Natural Philosophy," and 
"Wells' Science of Common Things." 

It has been the aim of the author to render these works, in the highest 
sense of the term, practical, and at the same time interesting to the student. 
Advantage has also been taken of the very latest results of scientific discovery 
and research. 



J* Y 



INDEX 






AcffTYLE, 444 

Acetates, 44T 
Acid, acetic, 445 

antimonic, 381 

arsenic, 382 

arsenious, 331 

benzoic, 473 

boracic, 27T 

butyric, 429 

carbonic, 290 

chloric, 24T 

chromic, 363 

citric, 452 

crenic, 425 

cyanic, 293 

ferric, 361 

flaosilicic, 280 

formic, 447 

fulminic, 299 

gallic, 454 

humic, 425 

hydrochloric, 242 

hydrocyanic, 298 

hydrofluoric, 25T 
hydrofluosilicic, 281 
hydrosulphuric, 266 
hypochloric, 247 
hypochlorous, 245 
hyponitric, 234 
hyposulphurous, 265 
lactic, 429 
mallic, 452 
manganic, 363 
margaric, 467-469 
muriatic, 242 
nitric, 228 
nitro-muriatic, 245 
nitrous, 234 
oleic, 467-463 
oxalic, 451 
pectic, 416 
phosphoric, 274 
phosphorous, 275 
prussic, 298 
pyroligneous, 410 
silicic, 279 
stearic, 467-469 
succinic, 473 
sulphindigotic, 460 
sulphuric, 262 
sulphurous, 260 
tannic, 452. 



Acid, tartaric, 452 
uric, 497 
valerianic, 449 
Acids, classification of, 178 
defined, 174 
vegetable, 450 
Acidification, theory of, 445 
Aconite, 457 
Acroleine, 470 
Actinism, 126 
Adhesion, 14 

and chemical action, 32 
force of, 33 

influence of on boiling point, 97 
Adipocere, 470 
Aeriform bodies, 18 
Affinity, characters of, 159 
defined, 16 

degrees of, how manifested, 160 
illustrations of, 16 
measure of the force of, 159 
Air, analysis of, 227 

composition of, 224 
does not exist without vapor, 92 
how heated, 72 
in water, 216 

influence of on boiling point, 9T 
organic bodies in, 226 
Alabaster, 343 
Albumen, 421 

animal, 482 
Albuminous substances, 423 

nutritive value o£ 
424 
Alchemists, viewB of, 15T 
Alcohol, 433 

absolute, 439 
amylic, 448 
methylic, 447 
sources of, 443 
wine, 439 
Alcoholometer, 28, 440 
Aldehyde, 445 
Alkalies, denned, 174 

general properties of, 342 
metals of, 32T 
organic, 455 
Alkalimetry, 338 

Alkaline earths, properties of, 330 
Allotropism, 183, 196 
Alloys, what are, 326 
Altitudes, how measured by boiling point, 

Alum, 351 



506 



INDEX. 



Alum baskets, how produced, 46 

relations to heat, 74 
Alumiua, 351 

•silicate of, 353 
Aluminum, 351 
Amalgams denned, 320 
Amalgamation, 388 
Amber, 472 
Amethyst, 279 
Ambrotypes, 400 
Ammonia, 340 

carbonate of, 340 
in air, 225 
Ammonium, 339 

chloride of, 340 
sulphide of, 342 
Ammoniac, Sal, 340 
Amorphous bodies, what are? 44 
Amyle, 447 

Analysis, proximate, 405 
Anhydrous, meaning of, 218 
Animal nutrition, 485 

organization, 482 
Anode and cathode, 141 
Antimony, 380 

wine of, 381 
Aqua ammonia, 342 

regia, 245 
Arabine, 416 
Arbor saturni, 160 
Ardent spirits, 438 
Argals, 452 
Argand burners, 321 
Aridium, 167 
Arsenic, 381 

tests for, 385 
Arsenious acid, 381 
Ashes of plants, 473 
Asphaltum, 412 
Aspirator, construction of, 22T 
Assaying, 394 

Athermanous substances, T4 
Atmosphere, history of, 223 

pressure of, 95, 96 
Atom, chemical meaning of, 172 
Atoms, estimated size of, 173 

what are, 13 
Atomic theory, 169 

weights, table of, 16T 
■Axes of crystals, 52 
Azote, 220 



B 



Balance, construction of, 26 

use of, 23 
Balsams, 473 
Barium, 343 
Barometer guage, 108 
Bases defined, 174 
organic, 455 
Basorine, 416 
Battery, galvanic, 142 

Bunsen's, 145 

Daniel's, 145 

Grove's, 145 

Smee's, 143 

sulphate of copper, 144 

trough, 143 
Bayberry tallow, 471 



Beaum6, registration of, 23 
Beer, 434 

lager, 436 
Bees-wax, 471 
Benzoine, 473 
Benzole, 411 
Bismuth, 3S0 
Bitumen, 412 
Black, Joseph, 223 
Bleaching, history of, 249 

theory of, 239 

powder, 246 
Blood, constitution of, 490 
Blow-pipe, 322 

oxyhydrogen, 20T 
Blue-pill, 356 
Bodies, compound, 10- 
Boilers, incrustations in, cause of, 215 

steam, construction of, 67 
Boiling, influence of atmosphere on, 95 
point, 91 

influence of adhesion on, 97 
air on water, 97 
Bombs, asphyxiating, 450 
Bones, composition of, 4S7 
Bouquet of winei, 438 
Boracie acid, 277 
Borax, 278 
Boron, 276 

Brain and nerves, 485 
Brass, 379 
Brandy, 439 
Bread, 440 

making, 441 
stale, 442 
toasted, 442 
Brewing, process of, 435, 436 
Bricks, composition of, 358 
British gum, 416 
Britannia metal, 377 
Brimstone, 258 
Bromine, 255 
Bronze, 379 
Brucia, 456 
Bullion, what is, 394 
Burning fluid, 463 
Butter, 489 
Butyric acid, 429 



Cadmium, 372 
Calcium, 344 

chloride of, 349 
Calico-printing, 459 
Calomel, 386 
Caloric defined, 56 
Calorimetry, 77 
Camphene, 463 
Camphor, artificial, 464 
common, 464 
Candle, chemistry of, 317, 313 

combustion of, 318 
Candles, adamantine, 469 
Capillary attraction, 14 

illustrations of, 15, 16 
Caoutchouc, 474 
Caramel, 419 
Carbon, 282 

a deodorizer, 288 



INDEX 



507 



Carbon, bi-sulphide of, 296 
Carbonates, 295 
Carbonic acid, 290 

solidification of, 293 
solvent properties of, 292 
Carbonic oxyd, 295 
Carburetted hydrogen (light), 300 

(heavy), 301 
Cartilage, 484 
Case-hardening, 366 
Caseine, 422 
Cassius, purple of, 393 
Catalysis, 161 
Celestine, 344 
Cell life, 40T 
Cells, formation of, 406 

size of, 406 
Cellular tissue, 407 
Cellulose, 407 
Cementation (of steel), 867 
Cements, 345 

and mortars, properties of, on 

what depend, 32 
hydraulic, 346 
Cerates, 471 
Charcoal, 287 

adhesive action of, 83 
Cheese, composition of, 489 
Chemical action a source of heat, 62 

what is, 21 
Chemistry defined, 21 

inorganic, 156 
Chlorate of potash, 186 
Chlorates, properties of, 247 
Chloric acid, 247 
ether, 448 
Chlorimetry, 246 
Chlorine, 235 

history and preparation, 235, 

236 
and hydrogen, 242 
compounds of, 241 
disinfecting action of, 240 
liquid, 237 
peroxyd of, 247 

relations to combustion, 237, 238 
solution, 237 
Chloroform, 448 
Chlorophyle, 460 
Chrome yellow, 369 
Chromium, 368 
Chyle, 493 
Chyme, 493 
Cinchonine, 456 
Cinnabar, 385 

Circuit, compound galvanic, 142 
Citric acid, 452 
Clay, 353 
Cleavage, 55 
Coal, anthracite, 286 
bituminous, 287 
mineral, 286 
origin of, 286 
gas, 303 

how measured, 306 
purified, 304, 305 
Cobalt, 370 
Cochineal, 459 
Cognac, oil of, 449 
Cohesion, 14 

and chemical action, 29 



Coin, standard silver and gold, 391 

Coke, 287 

Cold, greatest artificial, 60 

how obtained, 103 
what is, 57 
Collodion, 408 

process, in photography, 400 
Colophony, 471 

Coloring principles, organic, 457 
Colors, " fast," what are, 458 

of the solar spectrum, 124 
substantive and adjective, 453 
Columbium, 380 

Combination, chemical, cause of, 158 
Combustibles, what are, 312 
Combustion, 189, 307, 312 

and explosion, 313 
light of, 315 
products of, 314 
spontaneous, 189 
Compound Radicals, 404 
Compounds, chemical, 158 

nomenclature of, 
176 
Compression a source of heat, 62 
Concrete, 346 
Condensation defined, 89 
Conduction of heat, 63 

illustrations of, 63, 64 
Contagion, 431 
Convection, 68 

Cooking, adaptation of water for, 216 
Copper, 377 

acetate of, 379 
alloys of, 379 
nitrate of, 379 
oxyds of, 378 
sulphate of, 378 

prevention from corrosion by sea- 
water, 155 
Copal, 472 
Copperas, 362" 
Cordials, 465 
Corrosive sublimate, 886 
Cotton fibers, 407 
Cream of tartar, 452 
Creosote, 410 
Crocus, 361 
Crops, rotation of, 479 
Crystal, rock, 279 
Crystals, axes of, 53 

cleavage of, 55 

formation of in solid bodies, 50 
native, 50 

primary forms of, 52 
properties of, 44 
secondary forms of, 53 
what are, 44 
Crystallization, 44 

circumstances which influ- 
ence, 45, 46, 47 
purification by means of, 

47 
theory of, 62 
water of, 49 
Crystallography, 52 
Cryophorus, the, 103 
Capillation, 389 
Current, voltaic, what determines the AU 

rection of, 140 
Cyanogen, 296 



508 



INDEX 



Daguerreotypes, how taken in the dark, 129 

Daguerreotype process, 398 

Dal ton, Dr., originates the atomic theory, 

169 
Decay, 424 
Decrepitation, 50 
Deliquescence, 49 
Dew, formation of, 72 

never falls, T3 

point, what is the, 73 
Dextrine, 414 
Diamond, 282 
Diamonds, artificial formation of, 284 

form and weight of, 283 
Diastase, 415 

Diathermanous bodies, 74 
Diffusion of gases, 39 
Digester, Marcet's, 105 
Digestion, 492 
Dimorphism, 54 
Disease, occasion of, 433 
Distillation, 99 
Dobe'reiner's lamp, 206 
Donarium, 167 
Drummond light, 207 
Drying and distillation, 100 
Dye-stuffs, 459 



Earths, alkaline, 343 

metals of, 350 
Earthenware, 353 
Ebullition, conditions of, 94 

defined, 91 
Efflorescence, 49 
Elasticity, 17 
Electricity a source of heat, 62 

and chemical action, 131 
conductors and non-conductors 

of, 133 
fundamental law of, 132 
nature of, 130 

ordinary and galvanic, charac- 
teristics of, 146 
positive and negative, 132 
quantity and intensity of, 146 
two conditions of, 131 
velocity of, 134 
voltaic, 134 
Electrolysis and electrolytes, 150 
Electro-chemical decomposition, 148 

theory of, 
143 
metallurgy, 152 
plating and gilding, 153 
Electrodes, explanation of, 148 
Element, chemical, 156 
Elements, classification of, 157 

electro-chemical, order of, 151 

positive and negative, 137 
metallic, 324 
natural condition of, 157 
nomenclature of, 176 
number of, 9 
table of, 167 
Emery, composition of, 351 
Enamel, 357 



Endosmosis defined, 36 

illustrations of, 37 
Endosmotic action, influence of, 38 

force, 38 
English system of weights, 24 
Epsom salts, 350 
Eremacausis, 425 

Equivalent proportions, law of, 164 
Equivalents, chemical, practical illustra- 
tions of the use of, 183 
scale of, 166 
Essences, 461 
Essential oils, 461 
Ether, 443 

a form of matter, 19 
chloric, 448 
nitrous, 444 
cenanthic, 438 
sulphuric, 443 
varieties of, 444 
Ethyle, 443 
Eudiometer, 209 
Eupion, 410 

Evaporation, conditions of, 91 
defined, 91 
freezing by, 103 
Expansion by heat, force of, 79 

theory of, 77 
Extracts, fruit, 449 



Fallowing, 480 
Fats, 466 
Fermentation, 427 

acetous, 428 
alcoholic, 428 
viscous, 429 
Fibrine, 483 
Figures, sensitive, 93 
Filters, formation of, 36 
Filtrate, what is a, 36 
Filtration, cause of, 35 
Fire, theory of the ancients concerning, 80T 
annihilatore, 291 
damp, 300 
Fixed oils, 4C5 
Flax fibers, 407 
Flame, 59 

blow-pipe, 323 
oxydizingand reducing, 323 
structure of, 318 
Flannels, why used as protection against ex- 
treme temperatures, 66 
Flint, what is, 279 
Fluidity an effect of heat, 87 
Fluorine, 256 
Fluor-spar, 256 
Flux, definition of, 278 
Food, nature and functions of, 498 
Force converted into heat, 61 
definition of, 12 
indestructible, 19, 20 
varieties, 13 
Forces, classification of, 20 
molecular, 13 
natural, 12 
Forests, influence of on evaporation, 92 
Formic acid, 447 
Formyle, 443 



INDEX. 



509 



Fowler's solution, 382 
Freezing mixtures, 102, 103 
French system of weights, 24 
Friction, cause of, 32 

heat produced by, 61 
Frost, 73 
Fuel, economy of, 67 

how saved in culinary operations, 101 
Fuller's earth, 354 
Furnace, reverberatory, 337 
Fusel oil, 448 



Galena, 373 
Gallic acid, 454 
Galls, nut, 452 
Galvanic circuit, 139 

theory of, 139 
current, resistances to, 140 
Galvanism, 134 

how discovered, 135 
Garancine, 459 
Garlic, artificial oil of, 450 
Gas carbon, 286 

how differs from a vapor, 89 
illuminating, 302 
•« laughing," 232 
meter, construction of, 306 
origin of the term, 223 
Gases, absorption of by water, 112 
conduction of heat in, 65 
diffusion of, 39 
endosmotic action of, 39 
expansion of by heat, 81 
how heated, 69 
liquefaction of, 111 
management of, 196 
what are, 18 
Gasometers, 198 
Gauge, steam, 108 
Gelatine, 484 

Germination, conditions of, 434 
Gin, 439 

Glass and pottery, 355 
colored, 357 
crown, 355 
Hint, 356 
soluble, 280 
Glauber salts, 336 
Glow-worms, 114 
Glucose, 419 
Glue, 484 
Gluten, 422 
Glycerine, 467, 470 
Glycocoll, 485 
Gold, 392 

compounds of, 393 
fine, 394 
fulminating, 393 
leaf, 394 
Grain weight, how originated, 24 
Gramme, value of, 25 
Graphite, 285 
Gravitation, 12 

Gravity and chemical phenomena, 22 
Guano, 480 
Gum, 416 

Arabic, 416 
Senegal, 416 



Gum tragacanth, 416 

guiacum, 472 

resins, 473 
Gums, elastic, 474 
Gun-cotton, 407 

powder, 332 

expansive force of, I 
how manufactured, 
Gutta-percha, 475 
Gypsum, 348 



II 



Hair, composition of, 485 

dyes, 454 
Haloid salts, 179 
Hardness, how measured, 81 

scale of, 31 
Hartshorn, 340 

Hayes, Dr., on air in sea-water, 217 
Heat, absorption of, 72 

amount transmitted to the earth by 

the sun, 70 
analysis of, 127 
and chemical action, 56 
and cold, extremes of, produce similar 

sensations, 57 
apparent effects of, 77 
capacity for, 76 
communication of, 63 
diffusion of, 57 

disappearance of in liquefaction, 100 
vaporization, 101 
distinguishing characteristics of, 56 
effects produced by the absorption of 

102 
evolved by combustion, 313 
imponderable, 57 
latent, 56, 150 

how converted into sensible, 
114 
measurement, theory of, 82 
produced by chemical action, 62 
radiant, disposition of, 71 
ratio between sensible and latent, 110 
reflection of, 71 
refraction of, 127, 128 
Bources of, 60 
specific, 75 

standard for comparing, 75 
variations of, 76 
of atoms, 172 
theory of, 58 

mechanical, 58 
vibratory, 58 
transmission of, 74 
two conditions of, 56 
unit of, 61 

universal influence of, 75 
Hematite, 361 
Horny matter, 486 
Humus, 425 

Hydrate, what is an, 214 
Hydrochloric acid, 242 
Hydrofluoric acid, 257 
Hydrogen, 199 

chemical characteristics of, 208 
combustion of, 203 
explosive compounds of, 204 
peroxyd of, 218 



510 



INDEX. 



Hydrogen, phosphuretted, 275 
seleniuretted, 268 
sulphuretted, 266 
Hydrometer, 28 
Hydrosulphuric acid, 266 

practical value of, 29 
Hygrometer, Daniel's, 94 

hair, 93 
Hygrometers, principle and construction of, 

93 
Hypochlorous acid, 245 
Hyposulphites, 266 



Ice, heat required to melt, 101 

influence of wind on the formation of, 

92 
of salt-water, why fresh, 43 
cream, how frozen, 103 
Iceland spar, properties of, 119 
Ignis fatuus, 276 
Illumination, materials for, 81T 
Ilmenium, 380 
Incandescence, 59 
Incense, 473 
India-rubber, 474 
Indigo, 459 
Inertia defined, 11 
Ink, blue, 298 

printer's, 4G6 

why does not spread on sized paper, 36 
spots, removal of, 451 
Inks, composition of, 453 

sympathetic, 370 
InBulation, 133 
Iodine, 253 

distinctive test for, 256 
Iridium, 396 
Iron, 360 

cast, 362 

?;alvanized, 371, 155 
n the blood, 491 
malleable, 364, 366 
ores of, 361 
oxyds of, 360 
pyrites, 362 
specular, 361 
sulphuret, 362 
tenacity of, 325 
wrought, 364 

why adapted for castings, 49 
Isinglass, 484 
Isomerism, 182 

two conditions of, 182 
Isomorphism, 54 

examples of, 352 



Jelly, calves 1 foot, 484 
Joule's experiments on heat, 61 



Kakodyle, 450 
Kyanizing, 38T 



Lac, 472 
Lacteals, 491 
Lactic acid, 429 
Lactine, 420 
Lager beer, 436 
Lamp, Berzelius' spirit, 322 
Dobereiner's, 206 
safety, 320 

wicks, why not overflow, 35 
Lamp-black, 288 
Lamps, Argand, 321 
Lard, composition of, 470 

use of steam in manufacturing, 110 
Laudanum, 456 
Lavoisier, 310, 311 
Lead, 372 

action of on water, 373 
alloys of, 375 
carbonate of, 374 
chromate of, 369 
sulphate of, 375 
white, 374 
Lead pencils, how made, 286 
Lead tree, 160 
Leather, 453 

6mell of, when burned, cause of, 
222 
Lettuce, active principle of, 456 
Light, action of on chlorine and hydrogen, 
238 
matter, 116 
and heat, relations of, 59, 128 
artificial, requisites for the produc- 
tion of, 320 
corpuscular theory of, 113 
degradation of, 129 
decomposition of 124 
divergence of, 116 
Drummond, 207 
electric, 114 

influence of on vegetation, 130 
in its chemical relations, 112 
law of diminution of, 116 
magnetization of, 124 
most intense artificial, 114 
nature of, 112 
polarization of, 120 

how explained, 121 
polarized, beautiful phenomena of, 

how discovered, 122 
practical applications of, 

122 
properties of, 121 
properties of, 115 
propagation of, 115 
reflection of, 117 
refraction of, 118 

solar, calorific and chemical elements 
of, 126 
three principles contained in, 
126 
sources of, 113 
velocity of, 116 
undulatory theory of, 113 
Lignine, 409 
Lime, 344 

carbonate of, 346 
caustic, 844 



INDEX. 



511 



Lime, chloride of, 248 
gas, 349 

hyposulphite of, G49 
slacked, 345 
sulphate of, 348 
superphosphate of, 2T0 
Linseed oil, 466 
Liquefactioa defined, 89 
Liquids, cohesion of, how shown, 30 
conduction of heat in, 65 
expansion of, hy heat, 80 
how cooled, 81 
limpid, 30 
temperature of in the spheroidal 

state, 98 
vapor produced by different, 110 
viscous, 30 
what are, 18 
Liquors, artificial, 449 
Litharge, 374 
Lithium, 339 
Litmus, 175, 460 
Loam, 354 

Locomotive boilers, construction of, 67 
Luminosity defined, 117 
Lunar caustic, 390 
Lungs, structure and use of, 494 



Madder, 459 
Magnesia, 350 

carbonate of, 350 
sulphate of, 350 
Magnesium, 349 
Malleable iron castings, 365 
Malic acid, 452 
Malt, 435 
Manganese, 367 
Manures, 480 

animal, 480 
mineral, 481 
vegetable, 481 
Margarine, 466 
Marl, 354 
Marsh-gas, 300 
Mastic, 472 
Matches, 272 
Matter defined, 9 

divisibility of, 10 
ethereal condition of, 19 
indestructible, 19 
properties of, 21 
three forms of, 17 
Meaty- diseased, 433 
Meats, method of preserving, 439 
Mechanical "action a source of heat, 61 
Mercaptans, 449 
Mercury, 335 

alloys of, 387 
chlorides of, 3S6 
nitrates of, 387 
sulphide of, 387 
fulminating, 300 
Metal, fusible, 326 
Metalloids, characteristics of, 184 

enumeration of, 184 
Metals, action of nitric acid upon, 231 
classification of,- 327 
good conductors of heat; 64 



Metals, noble, 3S5 

of the alkalies, 327 

oxydation of, 183 

properties of, 325 

protection from corrosion by gal- 
vanic agency, 154 

transmutation of, modern views of, 
157 

strength of, how affected by vibra- 
tions, 51 
Meteors, composition of, 183 
Meter, gas, construction of, 306 
Meter, what is a, 25 
Methyle, 436 
Miasm, 431 
Mildew, 432 
Milk, 488 

swill, 439 
Mines, extinguishment of fires in, 291 
Minium, 374 

Moistening a source of heat, 63 
Molasses, 418 
Molecules defined, 10 
Molybdenum, 380 
Morphia, 455 
Mortars, 345 
Mother liquor, 48 
Mucilage, 416 
Muntz metal, 379 
Muriates, 242 
Music, how connected with the composition 

of the atmosphere, 226 
Musical tones of burning hydrogen, 206 



N 



Naphtha, 412 
Naphtaline, 411 
Nascent state, 162 
Natural philosophy, 20 
Neutral bodies, 175 
Nickel, 370 
Niobium, 380 
Niter, 331 

sweet spirits of, 444 
Nitrates, 231 
Nitric acid, chemical action of, 230 

history, properties, and prepa- 
ration, 228, 229 
Nitrogen and oxygen, compounds of, 227 

chloride of, 248 

deutoxyd of, 233 

history of, 220 

instability of, in composition, 221 

iodide of, 221 

origin of, in plants, 220 

preparation and properties of, 228 

protoxyd of, 231 

use of, in the atmosphere, 225 
Nitro-benzole, 411 

Nomenclature, chemical, origin of, 176 
Nordhausen sulphuric acid, 264 
Norium, 167 
Nutrition, 492 
Nux vomica, 456 



Ocean currents, influence and cause of, 69 
Ochres, 354 



512 



INDEX 



Odors, classification of, 465 
Oil, " coup," 411 
fusel, 448 
linseed, 466 
pine, 47 ± 
Seneca, 412 
Oils, drying, 466 

empyreumatic, 465 
fixed, 466 
mineral, 412 
unctuous, 466 
volatile, 461 
defiant gas, 301 
Oleine, 466 
Opium, 456 
Organic chemistry, 401 

bodies, nature of, 401 
substances, origin of, 403 
structure, 405 
Osmium, 396 
Oxalates, 451 
Oxalic acid, 451 
Oxyd defined, 176 
Oxygen, 184 

active and passive conditions of, 

193 
and respiration, 191 
daily consumption of, 196 
in combination, 192 
magnetism of, 192 
Ozone, 193 

physiological influence of, 196 



Palladium, 396 

Palm oil, 471 

Paper, 408 

touch-, 331 

Paradox, culinary, 96 

Parafine, 411 

Parchment, artificial, 408 

Parian, 359 

Pearlash, 330 

Peat, 426 

Pectin e, 416 

Pelopium, 380 

Pepsine, 493 

Percussion a source of heat, 62 
caps, 300 

Perspiration and evaporation, influence of, 
on animal heat, 104 

Petrifactions, 294 

Petrolium, 412 

Pewter, 377 

Pyrometer, Daniel's, 88 

Pyrometers, construction of, 87, 88 

Phlogistic theory, 307 

Phlogiston, 307 

Phosphorescence, 114 

Phosphoric acid, 274 

glacial, 274 

Phosphorus, 269 

allotropic, or amorphous, 272 
combustion of, in oxygen, 191 
influence of, upon iron, 365 

Phosphuretted hydrogen, 275 

Photographs in colors, 409 

on what principle formed, 129 
paper, 899 



Photography, 397 
Physics defined, 20 
Physiology, what is, 20 
Pig-iron, 364 
Pile, voltaic, 136 

Zamboni's dry, 138 
Pitch, 410 
Planetary spaces, estimated temperature of, 

60 
Plants, action of, on the atmosphere, 478 
contain nitrogen, 220 
contents of the cells of, 412 
essential immediate principles of, 

405 
evolve oxygen, 168 
mineral constituents of, 475 
nutrition and growth of, 475 
Plaster of Paris, 348 

a non-conductor of heat, 67 
Plating, 391 
Platinum, 395 

adhesive action of, 34 
sponge, effects of, 205 
Plumbago, 286 
Poison, " Woorara," 456 
Poisons, 430 

Polarization of light, 120 
Poles of a galvanic battery, 141 
Pomatums, 462 
Porcelain, 359 
Pores, 11 

of leaves, 476 
Porosity, what is, 11 
Potassa (potash), 329 

carbonate of, 330 
chlorate of, 186, 247 
caustic, 329 
chromate of, 369 
iodide (hydriodate)of,255 
nitrate of, 331 
prussiate of, 29T 
Eulphate of, 351 
Potassium, 327 

cyanide of, 298 
ferrocyanide of, 297 
ferridcyanide of, 298 
Precipitation defined, 42 

how effected, 42, 43 
Presence, " action of," 162 
Proof spirit, 439 
Proteine, 422 
Proximate principles, 405 
Prussian blue, 296, 297 
Prussic acid, 298 
Puddling, 364 
Pulse-glass, 96 

Pulverization, effect of, on adhesion, 33 
Purification by crystallization, 47 
Putrefaction, 425 
Putty, 466 
Pyrites, iron, 362 
Pyroligneous acid, 410 
Pyroxyline, 407 
Pytaline, 492 



Quartation, assaying by, 394 
Quinine, 456 



INDEX. 



513 



R 



Radiation, 69 

influence of color on, TO 
influence of surface on, 70 

Radiators, good and bad, 70 

Radical, chemical, 179 

Radicals, compound, 296 

Reactions and reagents, 181 

Rectification, 99 

Red colors, 459 

precipitate, 380 

Refraction, double, 119 
of light, 119 

Refrigerators, principle of construction of, 
66, 67 

Repulsion, 16 

illustrations of the force of, 17 

Resins, 471 

Inspiration, 495-496 

uses of, 496 

Rhodium, 396 

River-water, purity of, 213 

Rochelle salts, 452 

Roman cement, 346 

Roan, 471 

Rouge, 361 

Rubber, vulcanized, 474 

Ruby, composition of, 351 

Rupert' s drops, 357 

Russia sheet-iron, 365 

Ruthenium, 396 

Rum, 439 



Safety-lamp, Davy's, 320 
Saline springs, 213 
Saliva, 492 
Sal ammoniac, 340 

soda, 336 
Saleratus, 331 , 
Salinometer explained, 95 
Salted meats, use of, as food, 503 
Saltpeter, 331 

not explosive, 331 
Salt an antiseptic, 500 
common, 334 
rock, 334 

relations to heat, 74 
Salts, classification of, 178 
defined, 174 
haloid, 179 
of sorrel, 451 
Sandstone, what is, 279 
Sap of plants, what is, 412 
Saturation of liquids, 41 
Sausages, poisonous, 432 
Scagliola, 349 

Sea, " phosphorescence" of, 115 
transparency of, 212 
waters, composition of, 214 
Sealing-wax, 472 
Selenium, 268 
Serpentine, 349 

Sheet-iron, Russia, how made, 365 
Shellac, 472 
Shot, 376 
Silica, 279 
Silicon, or Siliclum, 279 



Silicon, fluoride of, 281 
Silver, 388 

chloride of, 391 
fulminate of, 300 
nitrate of, 390 
oxyds of, 389 
Silvering, 391, 392 
Sizing, 484 

Skin, composition of, 485 
Slag, 363 
Smalt, 370 

Smelting of iron, 363 
Snow, crystals of, 45 

line of perpetual, 76 
protecting influence of, 66 
Soaps, 467 
Soapstone, 349 
Soda-ash, 336 
Soda, biborate, 278 

carbonate of, 336 
caustic, 334 
nitrate of, 338 
sulphate of, 336 
powders, 452 
water, what is, 293 
Sodium, 333 

chloride of, 334 
Soils, origin of, 478 
Solids, conduction of heat in, 64 
expansion of, by heat, 78 

in crystallizing, 48 
variation of cohesion in, 31 
what are, 17 
Solution and chemical combination, 43 

defined, 41 
Soot, 287 
Soup, why retains heat longer than water, 

68 
Spar, heavy, 343 

Derbyshire, 250 
Specific, heat, 172 

gravity, 26 

of gases, how determined, 

29 
of solids and liquids, 27 
Spectrum, solar, 125 

fixed lines in, 125 
Spheroidal state, 98 
Spirits of wine, 439 
Spring, air of, why chilly, 104 
Springs, mineral, 213 
saline, 213 
thermal, 213 
Stalactites, 347 
Stalagmites, 347 
Starch, 413 

Stars, fixed, light of, 125 
Steam, curious experiments on, 109 
expansive force of, 106 
high-pressure, 109 
invisible, 90 
latent heat of, 101 
pressure of, when formed in open 

air, 106 
pressure, varying conditions of, 108 
relation between temperature and 

pressure of, 107 
rule governing the elasticity of^ 106 
6uper-heated, 110 
why adapted for cooking, 105 
Stearine, 466 

22* 



514 



IN DE 3U 



Steol, 365 
Strontium, 344 
Strychnia, 456 
Stucco, 349 
Sublimation, 99 
Substances, simple, 9 
Substitution, law of, 165 
Sugar, 417 

cane, 417 

grape, 419 

manna, 420 

milk, 420 

refining, 418 

boiling, 97 

of lead, 447 
Sulphates defined, 178 
Sulphides defined, 178 
Sulphites defined, 178 
Sulphur, 258 

allotropism of, 259 
flowers of, 258 
milk of, 260 ' 
oils containing, 464 
alcohols, 449 
Sulphuretted hydrogen, 266 
Sulphuric acid, 262 
Sulphurous acid, 260 
Surface action, 33 
Sun, character of the light-giving substance 

of, 122 
the, a source of heat, 60 
Symbols, chemical, 179, 180 
Sympathetic Inks, 370 
Syrup, " sugar-house," 418 



Talc, 349 

Tallow, 470 

Talbotype, 399 

Tannic acid, 452 

Tannin, 452 

Tar, coal, 411 
wood, 410 

Tartar, crude, 452 
emetic, 381 

Tartaric acid, 452 

Tellurium, 268 

Temperature defined, 57 

greatest natural, 60 

Tension, electricity, 146 
of vapors, 106 

Test papers, 175 
tubes, 185 

Thermometer, air, 87 

Breguet's, 86 
Centigrade, 84 
differential, 86 
Fahrenheit's, 87 
mercurial, 83 
metallic, 86 
Reaumur's, 84 
self-registering, 85 
spirit, 87 
what it informs us of, 83 

Tides, motion of, a source of heat, 62 

Tin, 376 

plate, 377 

Tinctures, what are, 440 

Titanium, 380 



Trough, pneumatic, 196 
Tungsten, 380 
Turpentine, crude, 463 

oil, or spirits of, 464 
Twaddell's hydrometer, 28 
Type-metal, 376 



Ultramarine, 354 
Uranium, 380 
Urea, 497 
Urine, what is, 497 



Vacuo, boiling in, 97 

Valerian, 449 

Vanadium, 380 

Vaporization defined, 89 

Vapors, comparative volume of, 90 

density of, 91 

diffusion of, 40 

elastic force of, 105 

expansion of, by heat, 81 

form at all temperatures, 90 

how heated, 69 

invisible, 90 

when cease to expand, 105 
Varnish, 473 
Vegetable acids, 450 

extracts, 457 
Vegetation, influence of light on, 130 
Verdigris, 379, 447 
Vermilion, 387 
Vinegar, 446 

wood, 446 
Vitriol, blue, 378 

green, 362 

white, 372 
Volatile bodies, 89 
Volumes, equivalent, 163 



W 



Washing fluids, 469 
Water, action of, on lead, 373 
air in, 216 

coloration of vast bodies of, 212 
composition of, 209 

how proved, 209 
decomposition of, 148 

by heat, 200 
heat produced in, by friction, 61 
history of, 210 
how heated, 68 
of crystallization, 49 
properties of, 211 
salt, freezing point of, 81 
Bolvent properties of, 217 
when attains its greatest density, 81 
when basic, 218 
when increases the intensity of a 

fire, 201 
unequal expansion of, 80 
Waters, comparative purity of, 212 
hard and soft, 215 
medicated, 462 



INDEX 



515 



Waters, relative fitness for use, 214 

spring, comparative purity of, 212 
Wax, 4T1 

shoemaker's, 472 
Weight, absolute, 26 

denned, 13 

compared with bulk, 26 

specific, 26 
Weights, French and English, 24, 25 

two great systems of, 23 
Welding, 326 

Wheat, composition of, 441 
Wind, influence of, on evaporation, 92 
Winds, how produced, 69 
Wines, 43T 
Wood, carbonization of, by steam, 110 

destructive distillation of, 409 
Wool, structure of, 486 



Woolens, why adapted for clothing, 65 

Wort, 435 

Woulfe's apparatus, 244 



Yeast, 42T 

powders, 442 
Yellow dyes, 460 



Zinc, 371 

sulphate of, 372 
white, 372 
amalgamation of, 14S 




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